Ingredient substitutions: Swap beef sirloin for chicken, tofu, or shrimp for a different protein option. Use whatever mixed vegetables you have on hand—snap peas, zucchini, or snow peas work well too! Optional variations: Try adding a sprinkle of sesame seeds or chopped green onions for added flavor and crunch. For spice lovers, a dash of red pepper flakes can elevate the dish. Storage or reheating tips: Store any leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the microwave for quick meals or in a pan for an even better texture.