ROAST BEEF & FRENCH ONION GRILLED CHEESE

Ingredients

One tablespoon(s)  olive oil 

One small onion, sliced

One tablespoon(s) malted unsalted butter or olive oil

One tablespoon(s) whole-grain mustard

Two ounce(s) Gruyere cheese, grated

Two slice(s) roast beef

One teaspoon(s) thyme leaves

Kosher salt

Pepper

Four slice(s) (1/2- inches-thick) rye bread.

Direction

Heat olive oil in a medium skillet over medium heat.

Add onion, season with 1/4 teaspoon each salt and pepper, and cook, covered, stirring occasionally for 12 minutes. Reduce the heat to medium low, stir in thyme leaves and cook, uncovered, stirring occasionally, until the onions are golden brown, 15 to 20 minutes more (add 1 tablespoon water to the skillet if the onions start sticking).

Brush one side of each slice of bread with butter or oil

Form sandwiches with the bread, whole-grain mustard, Gruyere cheese, roast beef, and the onion mixture.

Cook the sandwiches, covered, until the bread is golden brown and crisp and the cheese has melted 4 to 5 minutes per side.