Onion Soup with Gorgonzola Toast

Forget the standard Gruyere cap. This onion soup floats a slice of broiled Gorgonzola toast on top, and the funky, salty bite of blue cheese against sweet caramelized onions is a combination that just works.

The onions start covered to sweat out their moisture, then cook uncovered in butter until deeply golden. That two-stage process builds sweetness without burning. A spoonful of tomato paste stirred into the beef stock adds body and a subtle acidity that keeps the broth from tasting flat.

Don’t rush the caramelization. Those 15 minutes of uncovered cooking are where the flavor lives. The onions should be a rich amber, not just translucent. If they start sticking, that’s good. The browned bits on the bottom dissolve into the stock and deepen the whole pot.

Pro Tips

• Veal stock makes this soup noticeably silkier if you can get it. Beef stock is the solid backup.
• The flour and thyme cook together for a full 5 minutes before the stock goes in. This toasts the flour and removes any raw, pasty taste.
• Broil the Gorgonzola toast separately, then float it on the soup right before serving. This keeps the bread crisp longer than melting cheese directly in the bowl.
• Serve in warmed bowls. Hot soup in a cold bowl drops temperature fast.

Variations

• Mixed allium: Add sliced leeks or shallots alongside the onions for a more layered, complex sweetness.
• Stilton swap: Use Stilton instead of Gorgonzola for a slightly milder, creamier blue cheese finish.