Japanese Miso Soup with Tofu and Seaweed

Other Fast With Oil Published February 04, 2026

Miso soup is one of the simplest and most nourishing fasting meals in existence — fermented soybean paste dissolved in hot water with a few clean additions. It takes ten minutes, costs almost nothing, and delivers probiotics, protein, and a warmth that settles the stomach in a way few other foods can. In Japan it is eaten at breakfast, lunch, and dinner. During fasting, it works at any hour.

The critical rule: never boil miso. Boiling destroys the beneficial bacteria and dulls the flavor. Add it at the end, off the heat.

FASTING LEVEL: Fast With Oil (naturally oil-free — this works on strict days as-is)
SERVINGS: 4
TIME: 10 minutes

INGREDIENTS

- 4 cups water
- 1 piece (10cm) dried kombu seaweed
- 3-4 tablespoons white or red miso paste (or a blend)
- 1 block (200g) silken or soft tofu, cut into 1.5cm cubes
- 2 tablespoons dried wakame seaweed
- 2 green onions, thinly sliced
- 1 teaspoon soy sauce (optional)

METHOD

1. Place the kombu in a pot with 4 cups of cold water. Bring to a gentle simmer over medium heat — do not boil. Just before the water reaches a full boil, remove the kombu and discard it (or save it for another use). This is your dashi base.

2. Add the dried wakame to the hot broth. It will rehydrate and expand within 2 minutes.

3. Add the tofu cubes gently — they are fragile. Let them warm through for 1-2 minutes.

4. Remove the pot from heat. Ladle about 1/2 cup of the hot broth into a small bowl and add the miso paste. Whisk or stir until the miso is completely dissolved — no lumps.

5. Pour the dissolved miso back into the pot and stir gently. Taste and add more miso if needed, or a splash of soy sauce for depth.

6. Serve immediately, topped with sliced green onions.

NOTES

- White (shiro) miso is milder and sweeter. Red (aka) miso is deeper and saltier. A blend of both gives the best result.
- Traditional dashi uses bonito (fish) flakes — the kombu-only version here is perfectly fasting-appropriate and still flavorful. On fish days, you can add bonito flakes for a richer broth.
- For a more substantial meal, add cooked soba noodles, sliced mushrooms, or shredded napa cabbage.
- Miso paste keeps indefinitely in the refrigerator. Buy the largest tub you can find.
- Silken tofu gives a custard-like texture; firm tofu holds its shape better. Both work.