Add flour, butter, and salt to bowl of stand mixer. Using paddle attachment, mix on medium speed until butter forms pea-sized pieces. Start adding ice water and keep mixing until all water is incorporated and dough grabs onto paddle. Be careful not to overmix; you want to see small pieces of butter in the dough as this will ensure a flaky crust. Remove dough from mixer, wrap with plastic wrap, and let rest in refrigerator for 1 hour before rolling out.

Remove dough and let sit on counter for about 10 minutes. Then, using a rolling pin on a lightly floured surface, roll dough into a rectangular shape, about 3/16-inch thick. Carefully roll dough onto rolling pin and transfer to a half-sheet (13-by-18-inch) pan. Cut off excess dough and place lined pan in refrigerator for another hour to allow dough to relax. Make quiche filling.

Preheat oven to 375 degrees F. Once dough is relaxed and firm, line dough with parchment paper and fill with pie weights or beans, then par-bake pie crust until exposed edges are golden brown. Remove pie weights and prick holes in bottom of crust with a fork to release steam. Place crust back in oven until center is golden brown. Let cool before adding the filling.

Heat a heavy-bottomed pot over medium-high heat. Add cut bacon and cook until bacon is crispy and has rendered most of its fat. Stir in onions, salt, and pepper, and cook until onions are dark brown, about 15 minutes, stirring frequently. Cool bacon-onion mixture.

Using a whisk and in a medium sized bowl, beat eggs, then add milk, cream, and cheese. Add bacon-onion mixture to egg mixture. Stir in chives.

To make quiche: Preheat oven to 350 degrees F. Pour filling into pre-cooked quiche shell and bake for about 40 minutes, until filling is browned and firm to the touch. Test with a cake tester or small knife in the center. The knife should come out clean when quiche is ready. Allow quiche to cool to room temperature.