French onion soup is all about the onions, and we like to upgrade it by sweating shallots and sweet white Vidalias with butter, creating a creamy and slightly sweet base for rich garlic- and thyme-infused broth. Then we let the slow cooker do all the work.
Speaking of those onions, don't slice them too thin or too thick. Somewhere around a generous eighth-of-an-inch thickness is perfect.
Slow Cooker Double French Onion Soup
Recipe from the Tasting Table Test Kitchen
Yield: 4 to 6 servings
Prep Time: 10 minutes
Cook Time: 5 hours and 5 minutes
Total Time: 5 hours and 15 minutes
2 pounds sweet white onions (such as Vidalia), halved and thinly sliced (2 large onions)
¾ pound shallots, thinly sliced (8 to 10 small shallots)
2 thyme sprigs
1 garlic clove, smashed
1 bay leaf
3 tablespoons unsalted butter
¾ teaspoon kosher salt, plus more to taste
8 cups low-sodium beef broth
Freshly ground black pepper, to taste
1 large baguette, cut into ½-inch-thick slices
8 ounces Gruyère cheese, thinly sliced or grated
1. In a slow cooker, combine the onions, shallots, thyme, garlic, bay leaf and butter, and season with salt. Turn the slow cooker on high and cook until the onions are very soft and the garlic has disintegrated, 3 hours. Add the beef broth, season with a pinch of black pepper and continue to cook on high for 2 hours more. Makes about 10 cups French onion soup.
2. Meanwhile, about 30 minutes before serving, adjust the oven rack to the top portion and preheat the oven to 425°. On an aluminum foil-lined baking sheet, arrange 8 to 12 bread slices in a single layer and toast in the preheated oven until light golden brown, 5 minutes. Set aside and increase the oven temperature to the low broil setting.
3. On the baking sheet, place 4 to 6 oven-safe bowls and fill each to the rim with soup. Top with 1 or 2 slices of toasted bread and layer with cheese, completely covering the bread. Broil in the oven until the cheese is melted, 2 to 3 minutes. Serve with any extra bread for dipping.