1-First, preheat the oven to 375°F (190°C) and brush the partially baked pie shell with 1 tablespoon of mustard, then set it aside.

2-Next, melt 2 tablespoons of butter in a pan and sauté the finely chopped onion until it’s tender but not browned.

3-Combine the cooked onion with 1/4 cup of finely chopped fresh dill (or 1 teaspoon dried dill), 1 pound of coarsely chopped cooked asparagus, and 1 1/2 cups of grated old cheddar cheese, then spoon this mixture evenly into the prepared pie shell.

4-In a separate bowl, beat 4 eggs and add 1 cup of milk along with 1 teaspoon salt, 1/4 teaspoon pepper, a pinch of nutmeg, and a pinch of cayenne pepper, mixing well.

5-Pour this egg mixture over the asparagus and cheese filling in the pie shell.

6-Bake for 35 to 45 minutes until the quiche is just set, then let it cool for 10 minutes before serving.