By Rodrigo Manterola

Have you ever been so hungry you could eat a horse? Well in Mexico we say, “I’m so hungry I could eat rocks” 

And for all reasons, Mexican cuisine is vast. Fruits, exotic animals, even insects were part of the prehispanic menu.

If you find yourself in a traditional market in any of the 32 states of Mexico, you will see very exotic ways to feed the hungry, many of these ways unique to each state.

But no state in Mexico surpasses the state of Oaxaca in exoticism.

Caldo de Piedra 1
Cooked grasshoppers in Oaxaca By Nanahuatl - Own work, CC BY-SA 4.0,

Grasshoppers, ants, ant’s eggs, the list is long, and if you are a sensitive person (Foodwise) then you probably want to stick to the more conventional Mexican cuisine, try a Mole.

Flavors combine in a very unique way, (if you are of the sensitive type, skip the next paragraph…) 

You see, insects have a unique taste to them, some have a nutty, or smoky taste to them, others taste more like seafood, or even fruity. It depends on the insect and the cooking method.

Welcome back my sensitive ones…

Today we’re going to talk about a particular dish, worthy of a king, actually, according to historians, that’s exactly what it was, a dish served only to royalty or elite members of the Oaxacan prehispanic people now known as Chinantecos.

The Chinantecos

The Chinantecos call themselves “tsa ju jmí” which means “People of the old language”

Their history is fascinating, and they are considered one of the few ethnic groups that were not conquered by the Spaniards.

They speak many variations of an ancient language, which emanated from the oto-manguean language and is spoken by thousands of people in the incredibly extensive but rugged geography of Oaxaca.

And yes, they make the “famous” dish called, Caldo de Piedra, (Rock Soup)

What is Caldo de Piedra or Mexican Rock Soup?

Caldo de Piedra 2

For centuries, this was a plate for the kings, but during, and after the Spanish invasion, many of these groups of people survived by isolating themselves in the valleys and mountains of Oaxaca with very little influence from the Europeans. There they survived in their old ways, some communities even to this day; and while the old kings had died, the ritual continued by feeding their women with this feast.

For the Chinantecos, this is a plate served to honor respect and to honor their women. Not bad uh?

These prehispanic Romeos have turned this dish into a homage to their women, all of them, but mainly the one dealing with the house budget. 

In this video, you can watch the traditional way to make a Caldo de Piedra from Oaxaca. The video was made by Dir. Arturo Juárez Aguilar, and Sarah Borealis.

The video is entirely in the Chinanteco language, with Spanish subtitles. Sorry…

While the Chinantecos have evolved and their traditions have interlaced with modern catholicism, some things never change.

The Ingredients for a Rock Soup

  • Onion 
  • shallot
  • Mexican Tea (Known in Mexico as Epazote)
  • Cilantro (Coriander)
  • Chilli
  • Fish
  • Shrimp
  • Water

How much? 

Well, this depends on the method and how traditional you want to go. 

If you’re going to be cooking for a small crowd, something like 8 people,  in the traditional way (like in the video above), I recommend

  • Three large onions or 6 spring onions
  • Two shallots, or three garlic cloves
  • One bunch of Epazote “Mexican Tea” if you don’t have Epazote, you can use a small bundle of parsley, margorain,and bay leaves to season the soup
  • Chili up! But if you are not a “picante” kind of person, have just one whole serrano chili for flavor, and remove when serving
  • 6 medium size white-meat-fish chunks, fish like;  perch, sole, bass, cod, haddock, grouper, etc any fresh or saltwater white meat fish will do
  • Half a kilo of U-12 or similar size (Medium size) shrimp 
  • Enough water to cover all ingredients in the cooking hole


If you’re cooking each portion individually, you can customize servings down to the makings. So let your guests decide.


You want more onion? Go for it …no chili is a sacrilege in Mexico, but I understand. 

You get the idea. Rock Soup has to be made at the moment of serving, like Tempanyaki, but without the table, the stove, or a second chance.

How to make Mexican Rock Soup the strictly traditional way

The ingredients are very important, but the key factor here is the method, and the learning curve is sharp.

Prep Time: 3 minutes, plus 2 days…

While the cooking time of a Mexican Rock soup is allegedly 3 minutes, there’s a little more to it, and takes about a weekend to make Caldo de piedra the traditional way, if you consider the camping aspect of it. As you need to be next to a creek or a river with some particularities.

Once you’re there, locate a slow corner of the river and find shore-rock formations around it. 

If this doesn’t fit your local river specifications, add two more days to prep time, while you find a river that does.

The river should provide the water, and the protein in this recipe, that is fish, shrimp, or any edible species in the river. If your local river does not provide this, add 25 minutes stop at your nearest fish market.

Get the shrimp and white meat fish.

Back at the river;

  • Find a concave surface (shallow hole) carved on the rock formations and wash with river water, make sure no dirt, tree leaves, or any other elements are present.
  • Go fish the ingredients if you didn’t stop at the fish market, see you in 3 hours, if lucky.
  • Look for firewood and make a good fire not far from your cooking area, see you in 30…
  • Look for river stones, not too big, the size of a fist will do. Get at least 20 rocks.
  • Fill the shallow hole with river water
  • Chop all the ingredients and toss ’em in
  • When the fire is at its highest, about 45 minutes later, add the riverstone on top of the fire
  • Let them heat up for 2 hours
  • Add the boiling hot rocks into your soup and let it cook for 3 minutes.
  • Et voila! Your Mexican Rock soup is ready!

Now, I know that sounds like too much, but it’s what the Chinantecos of Oaxaca do indeed.

And that’s why this soup is so special, it is a ritual.

There are, of course, other ways to achieve similar results with a lot less rituality in mind, although it takes an effort to cook it even with modern technologies. You still need boiling hot rocks, and heating them up to the right temperature requires a lot of energy. But you can still try; I did.

How to make Caldo de Piedra the easy way


It will still feel like a hybrid between cooking at home and a barbecue when making Caldo de Piedra at home. You will need a barbecue or grill, and hot charcoal to prepare it.


  • Two large onions or 6 spring onions
  • Two shallots, or three garlic cloves
  • One bunch of Epazote “Mexican Tea” if you don’t have Epazote, you can use a small bundle of parsley, margorain,and bay leaves to season the soup
  • Chili up! But if you are not a “picante” kind of person, had just one whole serrano chili, and remove when serving
  • 6 medium size white-meat-fish chunks, fish like;  perch, sole, bass, cod, haddock, grouper, etc any fresh or saltwater white meat fish will do
  • Half a kilo of U-12 or similar size (Medium size) shrimp 
  • Enough water to cover all ingredients in the cooking hole

Same ingredients as before. And as before, the amounts per serving are up to you.

Prep time; 3 hours + 3 minutes


  • Barbecue or grill
  • 20 river stones, washed
  • 4 heat resistant soup bowls, gore, or wood works fine
  • Barbecue pincers 
  • Enough charcoal to burn for 3 hours

Cooking method

Prep your grill, and fire it up, let the charcoal burn for at least 45 minutes, or until red hot.

Add the stones to the grill so they fit on top of the red hot charcoal without suffocating the fire, and let it heat for 2 hours. Keep an eye on the temperature of the charcoal, keep it hot.

While this happens, serve a good Oaxacan Mezcal with a chaser of cold Mexican beer and go to the kitchen. Chop ingredients to bite-size and keep in the fridge while you wait for the rocks to be ready.

Serve another round and go check on the fire.

About two mezcals and three beers later your rocks should be hot and ready to serve.

Bring out all the ingredients from the fridge, and if you dare, grab another beer, although by now you’re probably singing “La Cucaracha” from the bottom of your lungs.

Bring all the ingredients to the table outside

Serve the ingredients you want per bowl, in the bowls.

Add water to cover the ingredients in the bowl.

Add salt and pepper to taste.

With your pincers, grab a stone and place it in the bowl, hear that rock sizzle! Place two more rocks in the bowl.

You may need between 3 to 4 rocks to cook a bowl of Caldo de Piedra, in about 3 minutes.


Soup is ready to eat, you can leave the stones there, just don’t eat them.

Garnish your bowl with fresh cilantro, and add a few drops of lime juice. 

Eat it with Tortilla or Tlayudas, more on this below.

Buen Provecho!

How to eat Caldo de Piedra

To eat Caldo de Piedra you need tlayudas, another Oaxacan staple. These are large tortillas partially toasted, and with a layer of refried beans, and whatever you can put in it, topped with lettuce or cabbage, avocado, and salsa. Like  tacos, tlayudas are very versatile. In this case they will carry fish and shrimp cooked in our soup.

Caldo de Piedra 3
Tlayudas By Bobak Ha'Eri, CC BY-SA 2.5,

You can do this with regular corn tortillas as well, but it won’t be the same.

How I Destroyed a Caldo de Piedra

A few years ago, Lorna and I went to visit Lorna’s old friend Martin to his house in the countryside of Devon; a beautiful, quintessential English village.

Farmhouses dating back to the 15th and 16th centuries all over the place, and a small pub right in the center of the town, and only two minutes walk from Martin’s house. That was part of the problem.

My Caldo de Piedra was a different kind of homage, my rock soup was in celebration of old friends and new friends.

An interaction of cultures, and sure, a good time.

It didn’t go well…

While the enjoyment of eating outside in the garden with great friends was insuperable, I’m still grateful Martin’s family had something else to eat besides the soup.

You see, those two hours you wait for the fire to be hot enough and ready, …we spent them at the local pub.

The pub is lovely, built in a seventeenth-century thatched building. The interior is rustic, with its low beams, flagstones, log fires, and photographs of village old-timers on red walls; not to mention the lovely weather that day, perfect to enjoy their tables outside. In my defense, it was easy to get comfy there. and I had an assistant watching the fire…

Anyways, three pints of Guinness later we went back to Martin’s to check on the rocks, they had been in the fire for more than two hours by then.

I did leave an assistant behind to keep things going, but she neglected the process.

Appearently, Missy, Martin’s dog was not a good idea for an assistant. She decided to forget about our project and go digging holes in the yard or something.

The recipe had to adapt to the ingredients available and while all of them were the best Tesco can offer, we did miss the epazote leaves and added celery because, why not. These crime to Mexican cuisine  was immortalized by Martin in a video.

I love and respect my culture and its richness. The next video is not intended to be other than entertainment; and while my intention was definitely to serve Caldo de Piedra to our hosts, I must say it was my first time. (making the soup, I have drank Guinness before)

Some pictures of that day

Rodrigo Makes Caldo de Piedra on Video

Thank you Martin for the video!

We may be posting a video of a second, and more serious attempt soon. In the meantime, don’t try this at home.