Step 1

Gather all the ingredients.

Step 2

Discard the bottom of the shimeji mushrooms and separate them.

Step 3

Discard the stem of shiitake mushrooms and cut the caps into slices.

Step 4

Discard the bottom of the cremini mushrooms and cut the caps into slices. Combine all the mushrooms on a plate/tray.

Step 5

Roll up the shiso leaves and cut them into julienned strips.

Step 6

Open the canned tuna and press the lid down to squeeze excess oil. Boil 4 QT (16 cups, 3.8 L) water in a large pot. Once boiling, add 1 ½ Tbsp salt.

Step 7

Cook the spaghetti 1 minute less than the package instructions (you will cook a bit more with the sauce). You should be able to finish the following step before the pasta is done cooking. If your pasta is done cooking first, reserve 4 Tbsp (60 ml) of pasta cooking water, drain, and set aside.

Step 8

In a large frying pan, heat the olive oil on medium heat and add all of the mushrooms.

Step 9

Sauté for 30-60 seconds to coat the mushrooms with oil, and then add the canned tuna.

Step 10

Season with freshly ground black pepper and kobucha (or kosher salt)

Step 11

Add sake, mentsuyu, and butter and mix all together.

Step 12

Reserve 4 Tbsp (¼ cup, 60 ml) of pasta cooking water and add to the pasta sauce.

Step 13

Taste the sauce and adjust if needed. At this stage, the sauce should have a strong flavorful taste, not bland. If your pasta is not done cooking, turn off the heat and cover so the pasta sauce will not evaporate.

Step 14

Drain the pasta into a colander OR scoop the pasta from the pot. Add the pasta to the sauce. Toss the sauce and pasta well.

Step 15

Transfer the pasta to individual plates and garnish with shredded nori seaweed and shiso leaves.

Step 16

You can keep the leftovers in an airtight container and store in the refrigerator for up to 2 days or in the freezer for a month.