Super Steak Sandwich

Ingredients

• 1/3 cup vegetable oil
• 1 cup beer
• 4 cloves garlic, chopped
• 1/2 teaspoon freshly ground black pepper
• 1 teaspoon salt
• 2 tablespoons Dijon-style mustard
• 2 beef flank steaks (1 pound each)
• 3 tablespoons butter
• 2 cups onions, sliced into thin rings
• 2 cups sliced mushrooms
• 1/2 teaspoon paprika
• 1 large loaf French bread
• cheese (your preference), optional