French Onion Soup with Caramelized Onions

Pro tips

• Caramelize onions low and slow over medium heat, stirring every 5 minutes to prevent scorching and build deep color—this is the foundation of the soup's flavor.
• Use homemade croutons for better texture and control; store-bought tend to absorb liquid too quickly and become soggy.
• Deglaze the pan with brandy or sherry after caramelizing onions to lift fond and add complexity before adding wine and broth.
• Top the soup just before serving so croutons stay crisp; add cheese while the croutons are hot so it melts evenly.

Substitutions

• Brandy or Sherry → dry white wine or beef broth (lighter, less depth of flavor)
• Swiss and smoked Gouda → Gruyère alone (traditional, nutty alternative)
• Fresh thyme and rosemary → 1 tsp dried herbs or Italian seasoning (reduce quantity; less aromatic)

Storage & make-ahead

Refrigerate the soup base (without croutons or cheese) in an airtight container for up to 3 days; reheat gently on the stovetop and add fresh croutons and melted cheese just before serving.

How long does it take to caramelize the onions?

Caramelizing onions typically takes 30–45 minutes over medium heat, stirring frequently to develop deep color and sweetness without burning.

Can I make French onion soup ahead of time?

Yes. Prepare the soup base (onions, broth, wine, herbs) up to 2 days ahead; refrigerate. Reheat gently before serving, then top with croutons and cheese.

What can I use instead of brandy or sherry?

Substitute with additional dry white wine (same volume) or beef broth for a less alcoholic version; the flavor will be lighter but still delicious.

Do I need both Swiss and smoked Gouda cheese?

No. Use either cheese alone, or swap for Gruyère, which is traditional and adds a nutty, complex flavor that pairs well with caramelized onions.