Plain Borth Soup Recipe

Combine liquids

In a large pot, pour 6 cups of water and 2 cups of low-sodium stock. Add the dried kombu if using. Bring the mixture to a gentle simmer over medium heat.

Once simmering, reduce heat to low so the liquid barely bubbles. Keep covered to preserve heat while you prepare the vegetables.

Prepare vegetables

Peel and finely dice enough yellow onion to measure 1/2 cup. Peel and grate or dice a medium carrot to yield 1/2 cup. Trim and finely dice one celery stalk to 1/2 cup. Mince 1 clove of garlic. Chop the parsley finely to yield 2 tablespoons.

Sweat aromatics

In a medium skillet or in the same pot over medium-low heat, melt 1 tablespoon of butter (optional for plain version, omit if strictly plain). Add the diced onion, carrot, and celery and a pinch of salt. Cook, stirring occasionally, until the vegetables are soft and translucent, about 6–8 minutes. Add the minced garlic and cook 30–60 seconds until fragrant.

Transfer the softened aromatics to the simmering stock. If you used kombu, remove it now and discard (or save for another use).

Let the soup simmer gently with the vegetables for 10–12 minutes so flavors meld.

Season and finish

Stir in 1 1/4 teaspoons salt and 1/4 teaspoon white pepper. Taste and adjust seasoning as needed. Add the chopped parsley and the 1/2 teaspoon lemon juice, if using, to brighten the soup.

If you omitted butter earlier and want a richer finish, stir in 1 tablespoon unsalted butter now until melted. Ladle soup into bowls and garnish with 1 tablespoon chopped chives or green onion per serving.

Serve hot. Store leftovers covered in the refrigerator for up to 3 days or freeze for up to 1 month.