Bone French Broth Onion Recipe

Slice the onions

Peel and cut the yellow onions in half from root to tip. Lay each half flat and slice thinly (about 1/8 inch). Aim for uniform slices so they caramelize evenly.

Cook onions low and slow

In a large heavy-bottomed pot or Dutch oven, melt the butter with the oil over medium heat. Add the sliced onions and sprinkle the sugar and 1 teaspoon of the salt over them. Stir to coat. Cook, stirring every 4–6 minutes, allowing onions to soften and turn a deep golden brown without burning. This will take 35–45 minutes. If the pan starts to smoke or the onions stick, reduce heat slightly and deglaze with a splash of water or a tablespoon of wine.

Season onions

When onions are richly caramelized (deep amber, sweet aroma), add the ground black pepper and the remaining 1/2 teaspoon salt. Stir and cook for 1 minute more.

Deglaze the pot

Increase the heat to medium-high and add the dry white wine to the pot with the onions. Use a wooden spoon to scrape up any browned bits on the bottom (these are flavor). Let the wine reduce by about half, about 2–3 minutes.

Add tomato paste and simmer

Stir in the tomato paste and cook for 1 minute to remove raw flavor. Add the beef bone broth, water, thyme sprigs, and bay leaves. Bring the mixture to a gentle simmer.

Simmer and adjust

Lower heat to maintain a gentle simmer and cook uncovered for 20–25 minutes to let flavors meld. Skim any foam or excess fat from the surface. Stir in Worcestershire sauce and cognac if using. Taste and adjust seasoning with additional salt and pepper as needed.

Prepare toasts

While the broth simmers, preheat the oven broiler (or a 450°F / 230°C oven). Arrange baguette slices on a baking sheet and toast under the broiler until golden on both sides, about 1–2 minutes per side. Alternatively, rub slices with a cut clove of garlic for extra flavor before toasting.

Assemble bowls

Remove thyme sprigs and bay leaves from the soup. For oven-proof bowls or ramekins, ladle hot soup into each bowl, leaving about 1/2 inch headspace for the toast and cheese. Float one or two toasted baguette slices on top of each bowl of soup.

Top with cheese and gratinate

Pile a generous amount of grated Gruyère over the toasts (about 1/3 cup per serving) and sprinkle a little Parmesan if using. Place bowls on a baking sheet and broil until cheese is melted, bubbly, and lightly browned, 2–4 minutes. Watch carefully to avoid burning.

Remove baking sheet from oven (use oven mitts) and let bowls rest for 1–2 minutes. Garnish with chopped fresh parsley. Serve the soups hot, with extra toasted baguette on the side if desired.