Preheat over to 375F. Line baking sheet with parchment paper.
Prick holes in crust with fork and blind bake for 10 minutes. Remove from oven and set on cooling rack while preparing quiche ingredients.
Drizzle butternut squash with olive oil, roast butternut squash for 25 minutes. While squash is roasting caramelize the onions.
In a pan heat up 1 tablespoon olive oil, add onions. Cook over moderate heat for 25 minutes. Add dash of balsamic at the end, cook for an additional few minutes to incorporate. Remove from heat.
Whisk together whole milk and eggs until a steady stream of pale yellow runs down the whisk (this is how you know the eggs are fully incorporated). Add rosemary, thyme, salt and pepper. Add butternut squash, onion, spinach, and desired cheese (up to 1 cup).
Pour into pie crust, but do not overfill. Bake 30-35 minutes until edges are golden brown and center is just set.
*Rosemary can be substituted for any herbs on hand such as basil, or sage
**Feta can be substituted for up to 1 cup of any desired cheese such as goat cheese, cheddar parmesan, or gruyere (goes especially well with sage).