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French Onion Soup

Deeply caramelized onion soup with beef broth, toasted bread and bubbling Gruyère.

Prep15 minCook100 minTotal115 minYield6 servingsLevelEasy

Source-reviewed. No original CookClue test is claimed unless it is actually recorded.

French onion soup with dark caramelized onions and a bubbling Gruyère toast

Before you start

What this method is trying to achieve

Caramelize the onions slowly to deep golden brown without blackening them, deglaze cleanly and finish each crock under the broiler.

Success looks like

Know the target before you cook

The broth should taste sweet-savory and concentrated, with no acrid bitterness and a browned melted cheese cap.

Ingredients

What you need

Base

  • 6 yellow onions, thinly sliced
  • 85 g unsalted butter

Aromatics

  • 2 sprigs thyme

Liquid

  • 1.4 L beef broth

Finish

  • 60 ml cognac or dry sherry

Serving

  • 6 slices French bread, toasted
  • 225 g Gruyère, shredded

Method

Cook by the cues, not just the clock

Caramelize onions

  1. Cook onions slowly until evenly deep golden brown.

Deglaze

  1. Add cognac or sherry and scrape up brown fond.

Simmer broth

  1. Add beef broth and thyme and simmer to marry flavors.

Toast bread

  1. Toast bread until dry and crisp.

Broil crocks

  1. Top soup with toast and Gruyère and broil until bubbling and browned.

Critical checkpoints

Stop here and check

other

Onions deep golden?

Onions are brown but not black.

Lower heat if dark spots appear.

other

Broth balanced?

Sweet onion flavor is stronger than acrid bitterness.

Taste before assembling crocks.

other

Soup bitter?

The soup tastes harsh or burnt.

Use french-onion-soup-bitter.

If yours looks different

Route the failure before changing the recipe

The finished soup tastes harsh, burnt or acrid.French onion soup bitter? Diagnose onion and fond scorching.

Why Does My French Onion Soup Taste Bitter?

After cooking

Storage, reheating & substitutions

Storage

Refrigerate soup base separately from bread and cheese.

Reheating

Reheat soup gently, then assemble and broil fresh.

Substitutions

Use Swiss cheese if Gruyère is unavailable.

Evidence

Sources & methodology

Technical claims and method decisions are tied to sources. Recipe-specific advice is not presented as a universal food-science law.

  1. French Onion SoupFood Network Kitchen

    Food Network caramelizes onions slowly, simmers with beef broth and tops with Gruyère toast.

    publisherPassage verified
  2. The Best French Onion SoupFood Network Kitchen

    Food Network recommends yellow onions and warns not to take them too dark.

    publisherPassage verified