Ingredients

  • 1/4 cup extra-virgin olive oil
  • 4 large onions, thinly sliced
  • 1/4 cup fino sherry
  • 1 1/2 teaspoons caraway seeds, lightly toasted
  • Kosher salt and freshly ground pepper
  • 12 slices of rye bread from a square loaf of rye or European pumpernickel bread
  • 1/2 cup whole-grain mustard
  • 10 ounces Gruyere cheese, coarsely shredded

Method

  • Heat 2 tablespoons of the olive oil in each of 2 large skillets.
  • Add half of the onions to each skillet and cook over moderately low heat for 1 hour, stirring occasionally, or until nicely browned.
  • Scrape all of the onions into 1 skillet.
  • Stir in the sherry and caraway seeds and cook until the sherry is completely absorbed, about 1 minute.
  • Season with salt and pepper.
  • Preheat the oven to 400.
  • Lightly spread 1 side of each slice of bread with the mustard and arrange on a large baking sheet.
  • Top with the onions and cheese.
  • Season with pepper.
  • Bake the open-faced sandwiches for 6 minutes, or until the cheese is melted and the edges of the bread are toasted.
  • Transfer the toasts to a cutting board and cut into triangles.