Start by prepping your crust. In a bowl, stir together your flour, salt, and rosemary. Rub your butter into your flour mixture until you have a sand-like consistency

Stir in your cold water (I like to put a few ice cubes in a glass before filling it with cold water to make sure it’s extra cold). Then press the dough into a ball until there are no more dry spots

Place your dough between two large pieces of parchment paper, and roll into a circle that’s ⅛” thick. Make sure your dough is an even thickness throughout

Gently peel the parchment back from the top layer, lay it back onto the dough, flip all of it over, and repeat with the bottom (now top) layer of parchment.

Removing one side of the parchment, carefully lay that side face down into a 10-inch pie dish and remove the top layer of parchment

Carefully shift the dough to ensure it lies flat in the pan and along the sides. If you have more than an inch excess, use a butter knife to cut away any extra and redistribute to other spots where the crust is shorter

Tuck under the excess dough around the edges to form your crust

Make a peace sign with your pointer and middle fingers on one hand, and place it along the edge of your crust. With the pointer finger of your other hand, point toward the center of the peace sign and pull back the dough in the center of your fingers. This will form a crimp. Repeat along the edge of your crust until complete

Place your pie dish with the crimped crust in the fridge for 15 minutes

Preheat your oven to 425°F

Once chilled, remove your pie dish from the fridge and prick the bottom and sides of your crust with a fork to prevent the crust from puffing when you bake

Crinkle a piece of parchment paper and lay it carefully in your dish before pouring in your baking weights

Bake your chilled crust for 11 minutes. Remove from the oven and carefully lift out the parchment paper and baking weights

Before returning your crust to the oven, crack one egg from your quiche mixture into a large mixing bowl, whisk, and use a pastry brush to brush a thin layer along the inside of your crust. This will help bake a barrier between your crust and filling to prevent a soggy bottom

Bake for an additional 7 minutes until the inside bottom of your crust is no longer wet-looking and has a slight golden hint from the egg wash. Cool completely before adding your below filling

Cut your onion in half lengthwise, then lay each half on the flat side and make a vertical cut down the middle, before slicing into ¼” slices. This will give you quarter-moon slices so the onions distribute better in your quiche

In a frying pan, add your olive oil and sliced onions. Place over medium heat and cook down, stirring occasionally, until deeply caramelized - about 35 minutes. Towards the end, be sure to stir regularly to prevent the onions from burning

Add in your minced garlic, stir, and cook for another minute before removing from the heat

Preheat your oven to 350°F

In the large mixing bowl with your one egg, crack in your remaining seven eggs, salt, pepper, rosemary, yogurt, and milk. Whisk until thoroughly combined. You can use an immersion blender for an extra creamy filling

Stir in ⅔ of your cheese into your egg mixture

Across the base of your cooled crust, sprinkle half of your onions and garlic in an even layer. Cover with the egg mixture, and top evenly with the remaining ⅓ of cheese and the other half of your cooked onions and garlic. Use a fork to shimmy around gently and make sure the cheese is mixed into the egg mixture (not just sitting on top of it)

Bake for 40-45 minutes, until the edges are set and slightly browned and the center of the quiche barely gives a wobble

Cool for 15 minutes, then cut and serve!