Mexican French Onion Soup Recipe

Melt the butter in a 4- to 5-quart heavy pot over medium-low heat. Add the sliced onions, thyme sprigs, bay leaves, and salt. Cook, uncovered, stirring frequently, for about 45 minutes.

Keep stirring until the onions are very soft and have turned a deep golden brown. This slow caramelization is what builds the base of the soup's flavor.

Stir in the flour and cook for 1 minute, stirring constantly. Pour in the wine and continue stirring for another 2 minutes. Then, add the beef broth, water, and pepper, and bring the soup to a simmer, uncovered, stirring occasionally, for 30 minutes.

While the soup simmers, preheat your oven to 350°F and place an oven rack in the middle position. Arrange the baguette slices in a single layer on a large baking sheet and toast them, turning once, until they are completely dry, which should take about 15 minutes.

Remove the toasted bread (croûtes) from the oven and preheat the broiler. Place your soup crocks in a shallow baking pan.

Discard the bay leaves and thyme sprigs from the soup. Divide the soup evenly among the crocks, then float one toasted croûte in each. Use a cheese plane to slice enough Oaxaca cheese (about 6 ounces total) to cover the tops of the crocks, letting the ends drape over the rims. Sprinkle with Parmigiano-Reggiano.

Broil the crocks 4 to 5 inches from the heat source until the cheese is melted and bubbly, about 1 to 2 minutes. Keep a close eye on it to prevent burning.