For the Crust
- Combine dry ingredients in stand mixer using paddle attachment.
- Add butter in 2-3 batches then add cold water, a little at a time, until dough begins to form.
- Divide dough in half and flatten into discs. Cover tightly in plastic wrap, and refrigerate for at least 30 minutes.
- Roll dough into a 10-inch circle on a lightly floured surface then press into pie pan. Fold excess dough along edges and crimp to form crust. Trim extra dough if necessary.
- Place in refrigerator and let rest at least 30 minutes.
For the Filling
- Preheat oven to 350 degrees.
- Cook onion in butter over medium heat until translucent, 4-5 minutes. Add remaining vegetables and sauté until tender. Salt and pepper to taste. Turn off heat and set aside to cool.
- Whisk eggs one at a time into heavy cream. Reserve ¼ cup to use as egg wash.
- Place vegetable mixture into crust then pour egg and cream over vegetables. Top with cheddar cheese.
- Gently brush crust with egg wash.
- Bake for 30 minutes then remove from oven, cover with aluminum foil, then bake for an additional 15 minutes, or until set.