Pre-heat oven to 375 degrees F.
Par-Bake (blind bake) your pie crust as directed below.
While your crust is being prepared, start your sausage filling. In a large skillet, crumble sausage and with chopped onions on medium-high heat until brown and the onions are translucent. Add garlic and cook for an additional 2 minutes. Remove sausage mixture from pan and put in large bowl.
Add the fresh spinach to the same skillet and cook until wilted on medium heat. Remove from heat.
Add spinach to cooked sausage mixture. Add 6 oz feta (about 1 cup), 1/2 cup shredded cheddar cheese, and spices. stir to combine and par-baked pie crust.
Combine eggs, milk/heavy cream, and salt and black pepper. Pour egg mixture over top of sausage mixture. Use a fork to let egg mixture go all around sausage filling.
Cook at 375 degree oven for 15 minutes. Add remaining cheddar to top of quiche and cook for an additional 25-30 minutes. Let rest for 10 minutes. Serve and enjoy this delicious quiche!