Five Onion Soup Gratinee Recipe

Prepare onions

Peel and thinly slice all five onions (yellow, sweet, red, shallot, green onion whites) to yield about 6 cups total. Keep the green onion tops separately for garnish if desired.

In a heavy-bottomed saucepan or Dutch oven set over medium heat, melt 3 tbs unsalted butter with 1 tbs neutral oil. The oil raises the smoke point so the butter won't burn while you caramelize.

Add all sliced onions and stir to coat with the butter-oil. Spread them evenly across the pot and cook over medium to medium-low heat, stirring every 4–6 minutes. Sprinkle 1/2 tsp sugar and 1 tsp salt over the onions to help draw out moisture and promote caramelization.

Cook the onions low and slow until deeply golden brown and very soft, about 35–45 minutes. Adjust heat so they brown steadily but do not burn. If the pan looks dry at any point, lower heat and add 1–2 tbs water to deglaze and prevent scorching. Towards the end, add 1/2 tsp freshly ground black pepper and taste; adjust salt as needed.

Once the onions are richly caramelized, increase heat to medium-high and add 1/2 cup dry white wine and 2 tbs dry sherry (if using). Scrape the bottom of the pan with a wooden spoon to release any browned bits (fond). Cook until the wine is mostly reduced, about 2–3 minutes.

Add 3 cups beef stock and 1 cup chicken stock to the pot along with 3 thyme sprigs, 1 bay leaf, and 1 tsp Worcestershire sauce. Bring the mixture to a gentle simmer, then lower heat to maintain a low simmer for 15 minutes to meld flavors.

Taste and adjust seasoning with additional salt and pepper if necessary. Remove and discard thyme sprigs and bay leaf before serving.

While the soup simmers, prepare the bread rounds: brush both sides of 2 slices of baguette with 1/2 tbs melted butter. Toast under a broiler or in a 375°F / 190°C oven until lightly golden, about 3–5 minutes per side. Alternatively, toast in a skillet until crisp.

Place the toasted baguette slices on top of a wide, ovenproof soup cup or small gratin dish that will hold about 1 cup (240 ml) of liquid. Ladle 1 cup of hot soup into the cup, leaving a little room at the top so broth doesn't overflow when cheese melts.

Evenly distribute the toasted bread on the surface, then sprinkle 3/4 cup grated Gruyère and 2 tbs grated Parmesan over the bread. Add a pinch of freshly ground black pepper.

Place the filled soup cup on a baking sheet and broil in the oven until the cheese is melted, bubbling, and develops light golden brown spots, 2–4 minutes (watch closely to prevent burning). Alternatively, use a kitchen torch to brown the cheese evenly.

Carefully remove the cup from the oven, let rest 1 minute, then serve hot. Garnish with a few chopped green onion tops if desired.