25-Minute Flounder Miso Soup with Snap Peas & Tofu
This easy flounder miso soup with snap peas, tofu, and wakame is a light, healthy Japanese fish soup ready in 25 minutes. Perfect for busy weeknights!
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Want a light, comforting dinner that tastes like it simmered all afternoon? This flounder miso soup delivers deep umami flavor in just 25 minutes: silky tofu, briny wakame, tender flounder, and crunchy sugar snap peas, all in one pot, with the miso stirred in off the heat for fresh flavor.
The Story Behind Miso Soup
Miso soup is one of Japan’s oldest comfort foods, dating back to the 12th century — in Japan it’s so beloved it’s traditionally eaten at breakfast, not just dinner.
A classic Japanese cooking rule: never boil miso — high heat dulls its delicate aroma, which is why this flounder miso soup gets its miso stirred in off the burner. Fun trivia: flounder (karei or hirame) has long been prized in Japan for its sweet, delicate flesh, and it cooks in barely two minutes — made for quick soups like this one.
Why You’ll Love This Flounder Miso Soup
- Ready in 25 minutes with one pot and minimal prep
- Light yet satisfying — ~135 calories per serving, packed with protein
- Naturally pescatarian; easy gluten-free with tamari-style miso
- Customizable — swap in white miso for a milder soup, or bok choy for snap peas
How to Make Flounder Miso Soup
Start by boiling the instant dashi packet for 3–5 minutes according to the package, then remove it. Add the green onions, firm tofu, and flounder, and simmer gently for a few minutes until the fish is opaque and flaky.
Meanwhile, wake up the wakame in warm water, then stir it in along with the snap peas and cook just until the peas turn bright green. Off the heat, whisk the red miso smooth with a scoop of hot broth and stir it back in. The result: a flounder miso soup that’s light, brothy, and deeply savory.
Tips and Easy Variations
- Pat the flounder dry and cut it into bite-size pieces.
- Soft tofu is silkier, but firm tofu — what I used — holds its shape and reheats well.
- Leftover flounder miso soup keeps one day in the fridge — reheat gently, never boil.
- For a milder bowl, swap half the red miso for white or awase.
- No flounder? Cod, tilapia, or sole work beautifully too.
Stock Your Pantry From My Amazon or Walmart Storefronts
Want to skip the ingredient hunt?
My Amazon and Walmart storefronts has a matching Idea list for this flounder miso soup — red miso paste, dried wakame, instant dashi packets, plus a soup pot, ladle, and fine-mesh strainer.
Grab what you need and dinner’s ready in 25 minutes.
A Book Worth Shelving: Japanese Home Cooking by Sonoko Sakai
If this gentle style of Japanese cooking speaks to you, try Japanese Home Cooking: Simple Meals, Authentic Flavors by Japanese chef Sonoko Sakai. Her dashi-based soups inspired this flounder miso soup — the perfect first Japanese cookbook. (Affiliate link; it supports the blog at no extra cost to you.)
Ready to Ladle Up Something Light?
Grab your soup pot, whisk that miso, and treat yourself to a warm bowl tonight. If you make it, leave a comment and tell me how it turned out — pin it for later and share it with a friend!
Flounder Miso Soup
A light Japanese fish soup with tender flounder, crisp sugar snap peas, firm tofu, and wakame. Instant dashi and red miso. Ready in 25 minutes.
Ingredients
- 1 packet instant dashi (for about 4 cups water)
- 9 oz flounder fillets, cut into bite-size pieces
- 1 cup sugar snap peas, trimmed and halved
- 3 1/2 Tbsp red miso paste
- 8 oz firm tofu, drained and cut into 1/2-inch cubes
- 1 Tbsp dried wakame seaweed
- 2 green onions, thinly sliced
- Optional: grated ginger, white pepper, or a few drops sesame oil
How to make it
- Boil the instant dashi packet in about 4 cups water for 3–5 minutes, then remove the packet.
- Add the green onion whites, tofu cubes, and flounder. Simmer gently 2–3 minutes, just until the fish is opaque and flakes. Do not boil hard or the fish will break apart.
- Meanwhile, cover the dried wakame with warm water and let it rehydrate about 5 minutes. Drain.
- Stir in the wakame and snap peas. Cook 1–2 minutes until the peas turn bright green but stay crisp.
- Turn the heat off. Whisk the red miso with a scoop of hot broth until smooth, then stir it back into the pot. Do not boil after adding miso.
- Ladle into bowls, top with the green onion greens, and serve right away.
Notes
- Flounder can be 8–10 oz. Red miso can be 3–4 Tbsp. Tofu can be 7–8 oz.
- Skin on the flounder is optional. Pat the fish dry before it goes in.
- Firm tofu holds its shape. A few drops of sesame oil at the end is optional.
- About $13 for the pot, or $3.25 a serving. Calories are an estimate without rice.
- Leftovers keep 1 day. Reheat gently and never boil.
