Seaweed Soup Recipe Vegan: Ocean Umami in a Light Broth

This vegan seaweed soup captures the essence of ocean umami in a delicate, nourishing broth. I’ve refined the balance of sea vegetables and aromatics to create a dish that’s both comforting and deeply flavorful.

With simple ingredients and 15 minutes of active prep, you’ll have a light yet satisfying soup that highlights the natural brininess of seaweed without overpowering the palate.

Ingredients for Seaweed Soup Recipe Vegan

Simple sea vegetables and aromatics create this light, oceanic broth with minimal effort.

The seaweed is non-negotiable here. Wakame and kombu bring that true ocean depth—look for them at Whole Foods or any Asian market (they’re usually in the international aisle). I grab mine from H Mart when I’m stocking up on other staples. Kombu often comes in big sheets, so one package lasts forever. Just make sure it’s not the salted kind, which can throw off the flavor balance.

No wakame? Dried nori sheets (the sushi kind) work in a pinch—just tear them into smaller pieces. Out of kombu? Shiitake mushrooms at half the weight add similar umami. The tofu can be swapped for mushrooms or edamame if you want more texture. For gluten-free, use tamari instead of soy sauce. And if you’re missing rice vinegar, a squeeze of lemon works (but the vinegar’s mildness is ideal).

Seaweed expands as it soaks, so don’t be alarmed by the small amount. This soup keeps 3-4 days in the fridge, but the seaweed gets softer the longer it sits. Freezes well for 2 months—just omit the tofu and add it fresh when reheating.

Step-by-Step Instructions for Seaweed Soup

This method builds layers of oceanic flavor with minimal effort—perfect for weeknight cooking.

Step 1: Bloom the Seaweed and Aromatics

Place the 1 piece Dried Kombu Seaweed and 0.5 oz Dried Wakame Seaweed in a large pot with the 6 cups Vegetable Broth. Heat over medium until small bubbles form at the edges—this takes about 5-7 minutes. You’ll see the seaweed expand and soften as it releases its natural glutamates into the broth.

Add the 4 cloves Garlic Cloves (minced finely) and 1 tbsp Fresh Ginger (grated). Let them steep for 2 minutes until the broth becomes fragrant. Don’t let it boil vigorously—gentle heat preserves the delicate seaweed flavors and prevents bitterness from the kombu.

Step 2: Build the Umami Foundation

Stir in the 2 tbsp Soy Sauce, 1 tbsp Mushroom Soy Sauce, and 1 tbsp Rice Vinegar. The vinegar brightens the earthy notes while the soy sauces deepen the umami. Taste the broth—it should be savory with a subtle tang.

Add the 8 oz Tofu (cubed) and 0.5 tsp Red Pepper Flakes. Simmer for 3-4 minutes until the tofu absorbs some flavor and the broth turns a rich amber. The tofu will firm up slightly but stay tender, soaking up the seaweed’s briny essence.

Step 3: Finish with Freshness and Balance

Drizzle in the 1 tbsp Sesame Oil and add the 4 whole Green Onions (sliced, white and green parts separated). Reserve the green tops for garnish. Season with 0.5 tsp Salt and 0.25 tsp Black Pepper, adjusting to taste.

Simmer for another 2 minutes until the white parts of the green onions soften slightly but retain a bite. The sesame oil adds a nutty aroma that complements the seaweed’s oceanic depth. Turn off the heat—the soup is ready when the flavors meld into a harmonious, light yet complex broth.

Step 4: Rest and Serve

Let the soup sit for 5 minutes off the heat. This allows the seaweed to fully hydrate and the flavors to develop further. The wakame will plump up, turning the broth into a silky, umami-rich liquid with visible strands of seaweed.

Ladle into bowls and garnish with the reserved green onion tops. Each spoonful should deliver a balance of briny seaweed, creamy tofu, and aromatic broth. Serve immediately while hot, as the seaweed texture is best when freshly hydrated.

Storing and Reheating seaweed soup recipe vegan

Refrigerator Storage

Let the soup cool completely before storing, which takes about 1 hour at room temperature. Transfer to airtight containers—I prefer glass for easy reheating. It keeps beautifully in the fridge for 3-4 days, though the seaweed softens slightly over time. ❄️

Freezer Storage

For longer storage, freeze without the tofu to maintain texture. Use freezer-safe containers or heavy-duty bags, leaving 1 inch of headspace for expansion. It stays fresh for up to 2 months. Label with the date for easy tracking.

Stovetop Reheating

Reheat gently over medium-low heat for 5-7 minutes, stirring occasionally. If the soup thickens, add a splash of water or vegetable broth. Add fresh tofu cubes during the last 2 minutes to warm through without overcooking.

Microwave Reheating

For single servings, microwave covered on 70% power for 2-3 minutes, stirring halfway. Add a few drops of water if needed. Avoid high power to prevent the seaweed from becoming mushy.

Make-Ahead Tip

Prep the broth base and seaweed mixture 1 day ahead, storing separately. On serving day, reheat the broth and add fresh tofu and garnishes. This keeps the tofu firm and the flavors vibrant. 💡

Frequently Asked Questions