Kings Flat Iron Steak Sandwich

Details

Ingredients

• 4 sandwich rolls, partially split
• 4 teaspoons softened butter
• 2 teaspoons garlic powder
• 2 tablespoons vegetable oil
• 4 (4 ounce) thinly-cut flat iron steaks
• ½ cup fresh spinach leaves
• 1 tomato, sliced
• 1 avocado, sliced
• 8 thick slices fresh mozzarella cheese
• 2 teaspoons balsamic vinegar, for drizzling