1/2 cup unsalted butter
4-6 large onions, sliced
1 carrot sliced
2 garlic cloves, chopped
2 fresh thyme sprigs
Kosher salt and freshly ground black pepper
3 heaping tablespoons all-purpose flour
2 quarts beef broth or stock
1lb stew beef cubes (optional)
1 baguette, sliced
1/2 pound grated Gruyere
Melt the stick of butter in a large pot over medium heat. Add the onions, garlic, thyme, and salt and pepper and cook until the onions are very soft and caramelized, about 25 minutes. Dust the onions with the flour and give them a stir. Turn the heat down to medium low so the flour doesn’t burn, and cook for 10 minutes to cook out the raw flour taste.
Season the remaining flour with salt and pepper. Toss the beef cubes and sear in a pot. Remove the beef cube. Now add the beef broth or stock, bring the soup back to a simmer, and cook for 10 minutes. Add the beef cubes and carrots and put in a 350 degree oven for 2 hour. Take out at ½ hours, add onions, season, to taste, with salt and pepper.
When you’re ready to eat, preheat the broiler. Arrange the baguette slices on a baking sheet in a single layer. Sprinkle the slices with the Gruyere and broil until bubbly and golden brown, 3 to 5 minutes.
Ladle the soup in bowls and float several of the Gruyere croutons on top.
Alternative method: Ladle the soup into bowls, top each with 2 slices of bread and top with cheese. Put the bowls into the oven to toast the bread and melt the cheese.