Can I skip the stovetop caramelizing and do everything in the slow cooker?

You can, but the onions will take much longer to properly caramelize and the flavor won’t be as deeply developed. Quick caramelizing on the stovetop then slow-cooking is the sweet spot.

What’s the best cheese for French onion soup?

Gruyère is classic for its nutty melting qualities; blending with Emmental and a little Parmesan gives complexity and a nice golden finish.

Can I make this on High for a shorter time?

Yes — you can cook on High for 4–6 hours. The Low, long-simmer method offers the most developed flavor, but High works in a pinch.

Is cooking sherry necessary?

It adds depth and helps to deglaze the pan. If you prefer, substitute a dry white wine, vermouth, or a small splash of balsamic for a different profile.

How do I avoid soggy bread?

Toast bread until crisp before floating it on the soup, and broil to melt cheese right before serving. That keeps the topping satisfyingly textural.

Easy Slow Cooker French Onion Soup Recipe — Perfect for Busy Nights

Description

This Slow-Cooker French Onion Soup makes deep, savory onion flavor with almost no fuss. Caramelize the onions on the stove, transfer them to the Crock-Pot with broth and aromatics, and let everything simmer until supremely rich. Top with toasted bread and a melted cheese crown for the classic finish.

Ingredients

Scale

6 tablespoons butter
4 large yellow onions, thinly sliced into rings
1 tablespoon granulated white sugar
2 garlic cloves, minced
½ cup cooking sherry (or a dry white wine/vermouth)
7 cups reduced-sodium beef broth
1 teaspoon sea salt, or to taste
¼ teaspoon dried thyme
1 bay leaf
8 slices French bread or baguette
½ cup shredded Gruyère
⅓ cup shredded Emmental (or Swiss)
¼ cup freshly grated Parmesan
2 tablespoons shredded mozzarella

Instructions

Warm a large, heavy pot over medium-high heat and melt the butter. Add the sliced onions and cook, stirring occasionally, until they turn soft and translucent — roughly 10 minutes.
Sprinkle the onions with the sugar, lower the heat to medium, and continue cooking slowly, stirring frequently, until the onions turn a deep golden-brown and develop jammy sweetness. This stage takes at least 30 minutes. Add the garlic and cook one minute more, just until fragrant. Bold tip: Low and slow caramelization is crucial — don’t rush it.
Pour the cooking sherry into the pot and scrape the pan bottom to lift the browned bits (that fond adds huge flavor). Let the alcohol steam off for a minute.
Transfer the onion mixture to the slow cooker. Add the beef broth, sea salt, thyme, and bay leaf; stir to combine.
Cover and cook on Low for 8–10 hours or on High for 4–6 hours, until the broth is deeply flavored and the onions are meltingly tender.
About 10 minutes before serving, set your oven broiler and position a rack roughly 8 inches from the heat source. Arrange the bread slices on a baking sheet and broil 1–2 minutes per side until toasted and golden.
Toss the Gruyère, Emmental, Parmesan, and mozzarella together in a bowl.
Ladle the hot soup into oven-safe crocks, filling each about three-quarters full. Float a toasted bread slice on top of each bowl and sprinkle roughly two tablespoons of the cheese blend over the bread.
Place the filled crocks on a sheet pan and broil just until the cheese melts, bubbles, and takes on a light golden crust — about 1–2 minutes. Watch carefully so it doesn’t burn.
Carefully remove the crocks (they’ll be very hot) and serve immediately.

Notes

Quick notes & swaps
- Substitute a dry white wine or vermouth if you don’t have cooking sherry.
- For a vegetarian version, use a robust mushroom or vegetable stock and add a splash of soy sauce or tamari for extra savory depth.
- If you prefer shredded single-cheese toppings, Gruyère alone works beautifully.
- Salt adjustment: Taste the soup after slow-cooking and season to preference because broth brands vary in saltiness.
Bold reminder: Toast the bread first so it holds up better under the cheese and doesn’t go mushy immediately.

Nutrition

Serving Size: 1 serving
Calories: 442
Fat: 16g
Carbohydrates: 57g
Protein: 18g