Three Onion Soup Recipe

Prepare onions

Peel and halve the onions. Slice each half into very thin half-moons so you end up with about 7 cups total of mixed thinly sliced onions (4 cups yellow, 2 cups sweet, 1 cup red). Thin, even slices ensure even caramelization.

Sweat and caramelize

Heat a large heavy-bottomed pot or Dutch oven over medium heat. Add vegan butter and olive oil. When the fat is shimmering, add all sliced onions, sprinkle with the sugar and 1 teaspoon of the salt. Stir to coat. Reduce heat to medium-low and cook, stirring every 5–7 minutes, scraping browned bits from the bottom, for 40–50 minutes until onions are deep golden brown and sweet. If they begin to stick or brown too fast, lower the heat; add a tablespoon of water to deglaze if necessary.

Add garlic and deglaze

Add the minced garlic and cook 1 minute until fragrant. Pour in the white wine (or vermouth) to deglaze the pan, scraping up the fond. Simmer until the wine has reduced by about half, 3–5 minutes.

Build the soup

Add the vegetable stock, soy sauce (or tamari), bay leaf, and thyme sprigs. Increase heat to bring soup to a gentle simmer. Reduce heat to low, partially cover, and simmer for 20 minutes to allow flavors to meld.

Finish and season

Remove and discard the bay leaf and thyme stems. Stir in the lemon juice and remaining 1/2 teaspoon salt (adjust to taste) and black pepper. Taste and adjust seasoning — more soy sauce for savory depth, more lemon for brightness. Keep warm while preparing croûtes.

Prepare bread

Preheat oven to 425°F (220°C) or set broiler to high. Arrange baguette slices on a baking sheet. Brush each slice lightly with olive oil and, if using, a little vegan butter for extra richness.

Toast bread

Toast the slices in the oven for 6–8 minutes, flipping once, until golden and crisp. If using the broiler, watch closely and toast 1–2 minutes per side until golden.

Top with cheese

Evenly distribute the grated vegan melting cheese (or grated Comté if not strictly vegan) over the toasted slices.

Melt cheese

Return the cheese-topped slices to the oven or broiler and heat until the cheese is melted, bubbly, and lightly browned on top, about 2–4 minutes under the broiler or 6–8 minutes in the oven. Remove and keep warm.

Assemble bowls

Ladle 1 to 1 1/4 cups of hot onion soup into ovenproof bowls (ramekins) if you plan to toast the croûtes under a broiler on top of the soup. Alternatively, place a toasted croûte on top of the soup at serving.

Add croûtes

Place one or two cheese-topped croûtes on top of each bowl of soup. If finishing under the broiler, set filled bowls on a baking sheet and broil just until cheese is bubbly, about 1–2 minutes—watch carefully. Remove from oven.

Garnish and serve

Sprinkle fresh thyme leaves over each bowl and finish with a pinch of flaky sea salt. Serve immediately with extra toasted bread on the side.