Ingredient substitutions: If sirloin steak isn’t available, consider using ribeye or tenderloin for a different flavor profile. Optional variations: Add a splash of Worcestershire sauce or soy sauce for an extra layer of flavor, or toss in some sliced bell peppers or mushrooms during cooking for added veggies. Storage or reheating tips: Store any leftovers in an airtight container in the refrigerator for up to 3 days. To reheat, warm them in a skillet over low heat until heated through.