This recipe (aside from the electronics) is derived from Joshua Weissman’s video, How to Make Real Tonkotsu Ramen.


Below are all materials you will need to prepare the soup.

Broth / soup

Ingredient Quantity Units
Pig trotters 3 lbs
Green onion 1 bunch
Yellow onion 1
Shallot 2
Knob ginger 2 inches
Ramen noodles 1 package

Chashu (Braised pork belly)

Ingredient Quantity Units
Pork belly 2 lbs
Soy sauce 1/2 cup
Mirin 3/4 cup
Sake 1 cup
Ginger knob 2 inches
Green onion 1 bunch
Glove garlic 5 cloves


Ingredient Quantity Units
Bonito flakes 1/2 cup
Kombu 3 pieces
Soy sauce 3/4 cup
Dried shiitake mushrooms 1/4 cup
Chashu braising liquid 1/4 cup

Electronics (Optional)

Ingredient Quantity
Raspberry Pi 1
DS18B20 Temperature Sensor Module Kit 1


Prepare electronics

So I was planning on monitoring the soup using the DS18B20 temperature sensor but it did not arrive in time so unfortunately I don’t have data from that. I also thought it might be cool to monitor if the water level drops below a certain level by taking advantage of the conductivity of the soup by placing two separated wires into the soup at the minimum desired level. If a current can be measured between them (broth is acting as the switch) you don’t need to replace the water. I had a difficult time positioning the wires consistently given the boiling liquid and required occasional mixing.

I believe this is is very possible but will require some more specific hardware and / or modification to the pot itself. Anyway, if full control over your soup is what you desire you can download the code I wrote in anticipation of doing this at this link.

Once everything is set up, it should text / email you if soup temperature or broth level gets too low.

Prepare broth

  1. Add 3lbs trotters to large pot. Cover with 2 inches of water and bring to a rolling boil for 10 minutes. Remove any residue that floats to the top with a spoon or mesh strainer.
  2. Empty 3lbs trotters and water into a strainer and rinse to clean.
  3. Place trotters back into the large pot and cover with 3 inches of water.
  4. Cut 1 bunch green onion into fourths and add to large pot.
  5. Cut 2 shallots into fourths, leaving skins on, and add to pot.
  6. Cut 1 yellow onion into fourths and add to the pot.
  7. Peel 2 2 inch knobs ginger, slice and add to pot.
  8. Peel 5 cloves garlic and add to pot.
  9. Bring water in large part to a rolling boil. Minimize temperature while still maintaining a low boil. This will be maintained for 12 hours. Stir pot around once an hour. Additionally, add water to restore original level whenever half of the water had been lost.

Prepare chashu

  1. Cut 1 bunch green onion into 2 inch sections.
  2. Peel 2 inch knob ginger and slice.
  3. Add 1 cup sake, the green onion, the ginger, 3/4 cup mirin, 1/2 cup + 2 Tablespoons soy sauce, four cloves of whole garlic, and 1/3 cup water to a large oven-safe pot.
  4. Roll the pork belly length wise and tie with kitchen twine into three separate segments. Place into the pot with other ingredients.
  5. Bring chashu to a boil, then low boil and then cover with a lid and place into a 300 degree oven for 3-3.5 hours. Baste every 30 mins.

Prepare the tare

  1. Add three 2 inch peices of kombu to a small pot.
  2. Add 3/4 cup water to the pot.
  3. Boil the water and then let kombu seep for 10 minutes.
  4. Add 1/2 cup bonito flakes to pot and let steep for 5 minutes.
  5. After the 5 minutes poor solution through a fine mesh sieve into a medium bowl.
  6. Add 3/4 cup soy sauce, 1/4 cup + 2 tablespoons mirin, 1/4 cup chashu braising liquid and 1/4 cup rehydrating liquid used for mushrooms to medium bowl. Stir and lightly salt.

Prepare toppings

This should be done within a half-hour of time to serve.

  1. Finely chop the green part of a green onion.
  2. Dehydrate shiitake mushrooms according to package directions.
  3. Prepare ice water bath.
  4. Bring small pot of water to boil. Add eggs and reduce heat to gentile bowl. Boil eggs for 6-7 minutes then place into ice bath.

Assembling the soup

  1. Boil ramen noodles according to package directions.
  2. Slice chashu into into 1/2 inch slices. If cold reheat in pan.
  3. Add tare to bowl to taste.
  4. Strain broth and add to bowl.
  5. Add soft boiled eggs, chashu, mushrooms and sliced green onion to broth.



Here are a few pictures of my results.

Chashu just out of the oven

Closeup glam shot of that molten egg and soup

Abusing portrait mode