Slow Cooker French Onion Soup

Slow Cooker French Onion Soup

This slow cooker French onion soup is ridiculously easy to make, mainly since it cooks in a slow cooker! After it's been simmering all day, you come home to an amazing aroma and a fabulous meal for a cold winter day. You do not have to caramelize the onions; you can melt the butter in your crockpot, stir in the onions to coat, add the remaining ingredients, and cook. However, caramelizing the onions makes for a much, much better soup!
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  1. Step 1

    Heat butter in a large, heavy pot over medium-high heat. Add onions; cook and stir until translucent, about 10 minutes. Sprinkle onions with sugar; reduce heat to medium. Cook, stirring constantly, until onions are soft and caramelized, at least 30 minutes. Stir in garlic and cook until fragrant, about 1 minute.
  2. Step 2

    Stir sherry into onion mixture; scrape the bottom to dissolve the small bits of browned food. Transfer onions into a slow cooker and pour in beef broth. Season with sea salt; stir in thyme and bay leaf. Cover and cook on Low for 8 to 10 hours or on High for 4 to 6 hours.
  3. Step 3

    Preheat the oven broiler about 10 minutes before serving. Set an oven rack about 8 inches from the heat source.
  4. Step 4

    Arrange bread slices on a baking sheet; broil until toasted, 1 to 2 minutes per side.
  5. Step 5

    Lightly toss Gruyere, Emmental, Parmesan, and mozzarella cheeses in a bowl. Fill oven-safe soup crocks 3/4 full with onion soup and float a bread slice in each bowl. Top each with about 2 tablespoons cheese mixture.
  6. Step 6

    Place filled bowls onto a baking sheet and broil until cheese topping is lightly browned and bubbling, about 2 minutes.