First peel the potatoes, cut into slices and cook in salted water (with a little sugar) until al dente. Cut the asparagus into bite-sized pieces and cook with the potatoes (they don’t take as long).
Grease a baking dish with butter and spread the potato-asparagus mixture in it. Beat the eggs well and mix well with the remaining ingredients. Spread over the vegetables.
Bake over medium heat.