This is an elegant side dish that you can serve as part of a Mexican menu for lunch or dinner. Nopal, or cactus, is a very common ingredient in Mexican cooking, and is quite versatile. Here we use nopal as part of a "souffle" with cheese, cream, and eggs. The soufle is baked in a puff pastry crust. The nopal can be substituted for other vegetables if you do not have nopal.