Basic Cheesy Spinach Quiche with Bacon

frozen pie crust (deep dish)

butter

medium yellow onion, finely diced

diced cooked ham ((I buy pre-diced from the grocery store))

slices bacon, cooked and crumbled

large eggs

half and half

kosher salt

black pepper

ground nutmeg

Gruyere cheese, shredded (divided)

box frozen chopped spinach, (defrosted and wrung out in paper towels to remove excess moisture)

chopped canned mushrooms (wrung out in paper towel to remove excess moisture)

fresh parsley, minced