Yes, you can cook the eisbein up to the point where they have been pressure cooked (before they are browned and crisped) and store them in a covered container in the refrigerator for up to 3 days. When you are ready to eat them, put them into your Ninja air-fryer and grill them according to the recipe instructions. You can also place them under a hot grill in the oven until they are crisp. Keep your eye on them, and turn them often. They burn easily.