Slow Cooker French Onion Soup
•Posted on June 23 2025

This rich, comforting French onion soup practically cooks itself. Sweet yellow onions slowly caramelize overnight, then simmer with beef broth, balsamic vinegar, and a splash of brandy for extra depth. Top it off with toasted baguette slices and melty Gruyère. It’s cozy, classic, and perfect for a make-ahead meal.
Ingredients
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3 lbs yellow onions, peeled, sliced, and quartered
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2 tbsp unsalted butter
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2 tbsp olive oil
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2 tsp kosher salt, plus more as needed
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Freshly ground black pepper
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10 cups beef broth
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2 tbsp balsamic vinegar
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3 tbsp brandy (optional)
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Optional garnishes:
• 4–6 toasted baguette slices per bowl
• ⅓ cup grated Gruyère cheese per bowl (1⅓–2 cups total)
• Chopped parsley
Instructions
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Add sliced onions to the Ceramic Inner Pot with butter, oil, salt, and pepper.
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Cover and cook on LOW overnight (up to 12 hours) until golden and soft.
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Stir in broth and vinegar.
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Cook using the SOUP preset for 6–8 hours. Season to taste and stir in brandy, if using.
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Preheat oven to 350°F. Ladle soup into oven-safe ceramic bowls and place on a baking sheet.
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Top each with a baguette slice and generous amount of cheese.
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Bake for 20–30 minutes until melted, then broil for 2–3 minutes until bubbly and browned.
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Let cool slightly before serving. Garnish with fresh parsley if desired.
Servings: Makes 6–8