Grilled Steak Sandwiches with Melted Onion Sauce

2 lbs flank steak, about 1-1/2" thick, trimmed
1 Tbsp brown sugar
2 gloves garlic, minced
1 tsp course salt
1 tsp coarsely-ground pepper
1 tsp olive oil
8 Cibatta Rolls, sliced

Melted onion Sauce:
2 Tbsp olive oil
4 large onions, sliced thinly
1 Tbsp brown sugar
Ľ c balsamic vinegar
Salt and pepper to taste

In a small bowl, combine sugar, garlic, course salt and pepper. Pat steaks dry, brush with oil and rub with sugar mixture. Marinate for 30 minutes or overnight. Meanwhile, cook the sauce: Heat 2 Tbsp oil in a large, deep skillet on medium high heat. Add onions and cook for 10 minutes. Reduce heat to medium and cook, stirring occasionally, for 30 minutes. Onions should be very brown. Add sugar and vinegar and cook gently, adding water as needed until onions are "melted". Season with salt and pepper.

To Freeze: Freeze in freezer safe container, separating meat, bread and sauce.

To Reheat: Grill steaks for 4-6 minutes on each side for medium-rare. Let steak rest on carving board while reheating sauce in a pan. Slice steak thinly on the diagonal. To serve, layer slices of steak on half a sandwich roll and top with onions and greens.