How to Make It
Preheat oven to 400°.
Pre-bake the crust: Roll dough to fit slightly larger than a 9-inch fluted tart pan. Press dough into fluted edges of pan, trimming off excess pieces if needed. Poke several holes in the crust with a fork. Line crust with parchment paper, and fill with pie weights or dried beans. Place pan on a foil-lined baking sheet. Bake 10 minutes. Remove weights and foil, and bake 5 more minutes. Cool completely on baking sheet on a wire rack (about 15 minutes). Reduce oven temperature to 375°.
Cook the mushrooms: Heat a medium skillet over medium heat. Pour in oil, add mushrooms, and saute until softened and browned, about 5 minutes. Set aside.
Prepare the custard: In a large bowl, whisk together eggs, milk, chives, nutmeg, salt, and pepper.
Assemble the quiche: Spoon the mushrooms, bacon, and cheese into the crust. Pour in egg mixture and carefully transfer to oven.
Bake until set (a knife inserted into the center should come out clean), about 35 to 40 minutes. Let cool at least 10 minutes. Cut into 6 wedges and serve warm or at room temperature.