If using the All-Butter Pie Crust, begin by making the dough and hydrating it in the fridge for about 2 hours.

Roll out one disc of pie dough to ⅛" thick, or unroll one pre-made pie crust.

Add the crust to the pie plate and press into the bottoms and corners, then crimp the edges. Freeze the crust for 15 minutes, then dock all over with the tines of a fork.

Preheat the oven to 375℉/190℃. Add a piece of parchment paper to the crust and fill completely with pie weights (or dried rice/beans).

Par-bake the crust for 15 minutes (5 minutes for pre-made), then carefully remove the weights and parchment. Whisk an egg white with a splash of water, then brush all over the bottom and sides of the crust.

Continue baking (no weights) for another 10 minutes (5 minutes for pre-made), then remove to a wire rack to cool. Reduce the oven temperature to 350℉/177℃.

In a large pan, fry the bacon over medium heat until browned and crispy. Remove the bacon to a plate with a paper towel and keep all the grease.

In the same pan, add the mushrooms and toss in the fat then let it sit for a few minutes without touching it until some of the water begins to release. Add the a sprinkle of salt and toss to coat, then let it sit again for another few minutes until cooked and browned. Transfer to the bacon bowl.

Add the onions and garlic (and a touch of olive oil or butter if there is no more grease in the pan) and cook until fragrant. Remove and mix it in with the bacon and garlic.

In a large bowl, whisk together the eggs, heavy cream, milk, and salt until no streaks of yolks or whites remain.

Add the slightly cooled vegetables and bacon to the pie crust, then sprinkle over the shredded cheese.

Carefully pour the egg filling into the pie dish. Top with sliced scallions (optional) and extra bacon crumbles.

Bake for 30 minutes in the center rack, then transfer to the bottom third of the oven for the final 10-15 minutes to ensure the bottom is fully baked.

The quiche is done when it's slightly puffy around the edges with a jiggle in the very center (but not sloshy).

Cool the quiche on a wire rack for 20-30 minutes, then slice and serve.