This recipe from Betty Rosbottom’s new book, Soup Nights, is the perfect antidote to cold winter nights. Betty shares a tip direct from Julia Child: “She suggests stirring some small strips of Gruyère into the soup before adding the toasted bread slices. Those little strips melt as the soup simmers in the oven, melding beautifully into the onion broth.” Read more about Betty’s new book on page 10. Serves 6.
2 quarts beef stock (find Betty’s recipe for Beef Stock on the Recipes page of our website)
4 tablespoons unsalted butter
2 tablespoons vegetable oil
3 pounds yellow onions, sliced ¼ inch thick, to yield 10 cups
1 teaspoon salt, more to taste
¼ teaspoon sugar, more if needed
¼ cup all-purpose flour
¾ cup dry white wine
Freshly ground black pepper
18 baguette slices, cut about ⅜ inch thick
3 to 4 tablespoons olive oil, plus more if needed
12 ounces good-quality aged Gruyère, grated to yield 1½ cups and the remainder cut into slivers ¼ inch by 1 inch long
In a 5-quart heavy pot (with a lid) over medium-low heat, heat the butter and oil. When hot, add the onions. Cover and cook, stirring frequently, 15 minutes.
Remove the lid and raise the heat to medium. Stir in 1 teaspoon salt, sugar, and flour. Cook, stirring constantly, scraping the bottom of the pan so that the flour does not burn, until the onions are rich golden (like the color of light brown sugar), 35 to 40 minutes or more. (While you are cooking the onions, the flour will start to darken too and the onions will cook down considerably. That’s OK.)
In another pot, bring the beef stock to a simmer.
When the onions are done, add the simmering stock and ½ cup of the wine. Season the soup with salt and pepper, and a pinch or 2 of extra sugar if desired. Simmer, partially covered, 40 minutes more. With a large spoon, skim off any foam that forms. Add the remaining ¼ cup wine and season the soup again with salt and pepper. (Soup can be prepared 3 days ahead. Cook to this stage, then cool, cover, and refrigerate. Reheat over medium heat.)
While the soup is simmering, prepare the baguette slices and the cheese topping. Arrange a rack at center position of the oven and preheat to 350°F.
Brush the baguette slices generously on both sides with olive oil and arrange on a rimmed baking sheet. Bake until slices are crisp, 4 to 5 minutes per side. Remove and cool. (Baguette slices can be prepared 2 days ahead; store in an airtight container at room temperature.) Retain oven temperature.
Arrange 6 ovenproof soup bowls or ramekins on a rimmed baking sheet and fill them ¾ full with the hot soup. Divide the slivered cheese among the bowls. Float 2 or 3 baguette slices on top of each serving, and sprinkle generously with some grated cheese. Depending on the size of your bowls or ramekins, you may have some soup, cheese, or croutons left over.
Bake the soup until the cheese has melted and is lightly browned, 15 minutes. Watch constantly. If desired, run under a hot broiler to brown more, 1 to 2 minutes.