Cut butter into ½" cubes, wrap in plastic wrap, place in freezer for at least 30 minutes. Once butter has chilled, combine dry ingredients for crust and cut butter into dry ingredients (using blender or pastry cutter) until the butter is broken down into pea-sized pieces. Add water to the mixture and knead until the dough just comes together when pressed between your fingers. Roll dough out on a floured surface and gather into a disc. Wrap disc in plastic wrap and place in refrigerator for at least 20 minutes to chill. Once dough has chilled, preheat oven to 425 degrees and roll out dough to fill pie pan. Bake crust until light brown, about 10-15 minutes. Set aside to cool.

Caramelize onions by melting butter in sauce pan over medium-low heat and stirring in sliced onions. Cook onions on medium-low heat until soft and caramelized, stirring occasionally (this will take about 60-75 minutes, add salt 15-20 minutes into cooking). Set caramelized onions aside.

Toss sliced sweet potatoes in olive oil and roast in 425 degree oven until they are soft and begin to brown, about 15-20 minutes.

After the crust, onions, and sweet potatoes are done, reduce or preheat oven to 375 degrees.

Layer the sweet potatoes along the bottom of the crust, cover in onions and gorgonzola cheese. Whisk eggs, milk, salt, pepper, and nutmeg together. Pour egg mixture into pie crust until pan is filled (you may have some egg mixture leftover)

At this point you can cover the quiche, place in refrigerator, and let sit for up to a day before baking.

To bake, place quiche pan on a baking sheet (to avoid spilling in oven). Bake for 45-55 minutes until filling appears firm. Remove from the oven and let sit for at least 10 minutes before serving.