French Onion Soup – Classic Gratineed Soup with Gruyère

Step 1 — Prep the onions
Peel and very thinly slice the onions into 2–3 mm half-moons so they caramelize evenly.

Step 2 — Start caramelization (10 minutes)
In a large heavy pot over medium heat, melt the butter with the olive oil. Add onions and a pinch of salt. Stir to coat. Cook 10 minutes, stirring every 2–3 minutes, until they begin to soften and release juices.

Step 3 — Deep caramelization (20–30 minutes)
Reduce to medium-low. Add sugar (optional). Continue cooking 20–30 minutes, stirring frequently and scraping browned bits (fond) from the bottom. Aim for a deep golden-brown/mahogany color; if browning too fast, lower the heat. Do not burn.

Step 4 — Garlic & deglaze (4–6 minutes)
Stir in minced garlic; cook 30–60 seconds until fragrant. Increase heat to medium, pour in white wine, scraping up all fond. Simmer 3–5 minutes until reduced by about half (no harsh alcohol smell).

Step 5 — Broth & herbs (20–25 minutes)
Add beef broth, bay leaf, and thyme. Bring to a gentle simmer, then cook 20–25 minutes partially covered. Season to taste with salt and black pepper. Remove bay and thyme sprigs before serving.

Step 6 — Toasts (while soup simmers)
Preheat oven to 200°C / 400°F. Arrange baguette slices on a tray; toast 5–7 minutes until dry and lightly golden. (Optional: rub with cut garlic clove.)

Step 7 — Gruyère topping
Top each toast with grated Gruyère and return to oven 2–3 minutes until just melted (or do this under the broiler for 1–2 minutes—watch closely).

Step 8 — Assemble & gratinée
Preheat broiler/grill (high). Ladle hot soup into oven-safe bowls on a baking tray. Float 1–2 cheese toasts on each bowl; sprinkle extra Gruyère to blanket the top. Broil 1–3 minutes until cheese is bubbling and golden. Rest 2 minutes (very hot), then serve.