Prepare pie crust as directed. Remove from oven and set aside to cool.
In a large flat-bottomed fry pan, melt the olive oil and unsalted butter. Cook the onions over low-medium heat, until softened, about 15 minutes. Add cubed ham to pan and cook for 5 minutes more. Remove from heat.
Preheat oven to 375.
In a medium bowl, whisk togehter the egg, milk, cream, and parsley and season with salt and pepper.
Spread the onion and ham mixture in the cooked and cooled pie crust. Pour the egg mixture over the top.
Place on a baking sheet. Bake in a preheated oven for 50-55 minutes.