Allow crust to sit util soft enough to work. Spread in 9″ pie or quiche pan.
In a skillet, melt butter over medium heat. Add onion; cook, stirring occasionally, until softened, 6 to 8 minutes. Remove from heat; cool. (I don’t usually cool much, not sure how important that is.)
Preheat oven to 375F. Sprinkle 1/2 of the cheese over the crust. Top with onion, then ham. SPrinkle with remaining cheese.
Whisk together eggs, egg yolks, half & half, cream, salt, cayenne pepper, and nutmeg. POur egg mixture over ham and cheese.
Bake quiche until golden brown and custard is set, 35 to 45 minutes. Lert rest 5 minutes.