To “blind bake” the pie crust, heat your oven to 400 degrees and butter a 9” pie dish. Lay the dough into the prepared dish and crimp the edges if desired. Place a piece of parchment paper or foil in the center of the dough. Then pour pie weights or dry beans into the pie plate to weigh the crust down as it bakes. Bake for 10 minutes, then remove the pie weights and bake for another 5 minutes, until the crust is just beginning to brown. Remove from the oven while you make the filling.
Heat a large skillet over medium heat and add 1 Tbsp butter. Add the leeks and sauté for about 2 minutes until slightly translucent. Next add the sliced mushrooms. Sauté for an additional 2-3 minutes until the vegetables are soft and caramelized. Add the minced garlic, salt and pepper, and cook for another minute. Turn off the heat.
In a seperate bowl, whisk together the eggs, cream, milk, and parmesan cheese.
Combine the egg mixture with the sautéed vegetables and pour into the prebaked pie shell. Bake the quiche at 350 degrees for 25 to 30 minutes until the center is set and the top is golden brown.
