Pre-heat oven to 375°.
In the bowl of a stand mixer, using paddle attachment, cut chilled butter into the flour until small pea-sized pieces form (or use pastry blender or two knives). Slowly add ice water just until dough comes together (not sticky). Add 1 tsp additional water at a time if dough is too dry. Do not over-handle dough.
Divide dough in half if making double recipe. If making single crust, use all of the dough. Roll between sheets of parchment or plastic wrap, to about 1/8" thick. Peel off top layer and invert the dough into lightly greased pie plate. (Cover and chill if dough is too soft.)
Over medium-high heat, sauté broccoli with onion, garlic and olive oil for 5 minutes
Whisk eggs, milk, cheese, and salt and pepper in a large mixing bowl. Add veggies, and pour the entire mixture into the un-baked crust. Bake everything for 40-45 minutes .