Roll pastry to a 13-inch circle; ease into a 9-inch deep-dish pie plate, being careful not to stretch pastry. Trim pastry to 1/2 inch beyond edge of pie plate; fold under extra pastry. Flute edge. (Or fit pastry into a 9-inch pie plate and flute edge high.) Line the pastry in pie plate with a double thickness of foil. Bake in a 450 degree F oven for 8 minutes. Remove foil; bake for 4 to 5 minutes or until the pastry is set and dry.
Meanwhile, in a saucepan, cook asparagus in a small amount of boiling water for about 5 minutes or until just crisp-tender. Drain thoroughly. Arrange asparagus in bottom of pastry shell; sprinkle with cheese.
In a mixing bowl, beat eggs. Blend in sour cream. Then, stir in milk, onion, salt, and pepper. Pour over asparagus and cheese in pastry shell.
Bake in a 375 degree F oven for 35 to 40 minutes or until a knife inserted near center comes out clean. If necessary, cover edge of crust with foil to prevent overbrowning. Remove from oven; let stand for 10 minutes before cutting into wedges. Makes 8 side-dish servings.
To prepare the asparagus, wash and scrape off the scales, if you like. Break off the woody bases at the place where the spears snap easily.
In a bowl stir together flour and salt. Using a pastry blender, cut in shortening until pieces are pea-size. Sprinkle 1 tablespoon of water at a time over the flour mixture, tossing with a fork until all of the dough is moistened. Form dough into a ball.