Equipment
Ingredients
Broth Base
- 1200 ml water, cold
- 15 g dried kombu
- 20 g fresh ginger, peeled and sliced into thick coins
- 45 ml tamari
- 5 ml toasted sesame oil
Vegetables and Protein
- 200 g daikon radish, peeled and cut into half-moons
- 100 g fresh shiitake mushrooms, stems removed, caps sliced
- 300 g firm tofu, drained and cut into 2 centimeter cubes
- 150 g baby bok choy, washed thoroughly, halved lengthwise
- 30 g scallions, thinly sliced
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 107 kcal
- Protein
- 10 g
- Carbohydrates
- 9 g
- Fat
- 5 g
- Fiber
- 3 g
- Sugar
- 3 g
- Sodium
- 693 mg
- Saturated Fat
- 1 g
- Monounsaturated Fat
- 1 g
- Polyunsaturated Fat
- 2 g
- Potassium
- 465 mg
- Calcium
- 225 mg
- Iron
- 2.3 mg
- Magnesium
- 64 mg
- Phosphorus
- 165 mg
- Zinc
- 1.2 mg
- Vitamin A
- 88 mcg
- Vitamin C
- 30 mg
- Vitamin D
- 0.1 mcg
- Vitamin E
- 0.1 mg
- Vitamin K
- 37 mcg
- Vitamin B6
- 0.3 mg
- Thiamin
- 0.09 mg
- Riboflavin
- 0.17 mg
- Niacin
- 1.9 mg
- Folate
- 70 mcg
- Water
- 489 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Wipe the kombu gently with a damp cloth to remove any debris, leaving the white umami powder intact. Place the cold water, kombu, and ginger slices into a large pot and let it sit off the heat for 10 minutes to begin infusing.
Place the pot over medium heat and slowly bring the liquid to a bare simmer, aiming for about 65°C or 150°F. Just before the water reaches a rolling boil, immediately remove the kombu using tongs to prevent the broth from becoming bitter and slimy.
Stir in the tamari, daikon radish, and shiitake mushrooms. Maintain a gentle simmer for 15 minutes, or until the daikon is completely tender and translucent.
Gently lower the cubed firm tofu into the simmering broth. Cook for 4 minutes to warm the tofu through completely without breaking it apart.
Add the halved baby bok choy to the pot and simmer for 2 minutes until the leaves are bright green and wilted, but the thick stems remain slightly crisp. Remove the pot from the heat.
Carefully divide the hot vegetables, tofu, and broth among four bowls. Garnish with thinly sliced scallions and a few drops of toasted sesame oil if using. Serve immediately.
Chef's Notes
- The white powder on the surface of dried kombu is crystallized glutamic acid, which provides the deep umami flavor. Never wash it off under running water; simply wipe the kelp gently with a lightly damp cloth.
- For an even deeper flavor foundation, you can cold-brew the dashi by soaking the kombu in the water overnight in the refrigerator before proceeding with the heating steps.
- Adding the bok choy at the very last moment ensures it retains its vibrant green color and crisp texture, contrasting beautifully with the soft tofu and tender daikon.
- Tamari is used here to keep the recipe gluten-free, but if dietary restrictions are not a concern, traditional Japanese soy sauce works perfectly and provides a slightly sweeter, less earthy profile.
Storage
Refrigerator: 3 days — Store bok choy separately from the broth if possible to prevent overcooking upon reheating.
Reheating: Reheat gently on the stovetop over medium-low heat until simmering.
Troubleshooting
Broth tastes bitter, heavily oceanic, or has a slimy texture
Cause: The kombu was boiled at a high temperature or left in the broth for too long
Fix: Cannot be fixed
Prevention: Always remove the kombu just before the water reaches a rolling boil
Bok choy is mushy and has lost its bright green color
Cause: Overcooking in the hot broth
Fix: Cannot be fixed
Prevention: Add the bok choy at the very end of cooking, just moments before serving
Cultural Context
Kombu dashi is the foundational vegan stock in Japanese temple cuisine, known as shojin ryori. By combining this mineral-rich sea kelp with warming ginger and seasonal vegetables, this one-pot soup exemplifies the Japanese culinary philosophy of balancing nutrition, aesthetics, and harmony of flavors.
