Beer Marinated Flank Steak

1 large onion, thinly sliced
2 cloves garlic, thinly sliced
1/2 cup beer
1 tablespoon brown sugar
1 tablespoon Dijon mustard
2 tablespoons soy sauce
Freshly ground pepper
1 1/2 pound flank steak
Salt to taste
2 tablespoons butter

In a bowl, combine onions, garlic, beer, brown sugar, mustard, soy sauce and seasonings. Score one side of steak with 3 slashes. Place steak in large dish and pour marinade over steak. Marinade 2 hours. If marinade does not cover steak completely, turn it once.

Grill or broil steak about 3 minutes per side or until medium-rare. Place on cutting board, let sit for 15 minutes; salt and thinly slice against the grain.

While steak is grilling, pour marinade ingredients into a pot. Boil for 3 minutes, or until sauce is slightly thickened. Reduce heat to low, add butter and stir into sauce until incorporated. Serve over steak. (Serves 4 to 6)