Dice the Butter (1 cup).
In a large bowl, whisk together All-Purpose Flour (1 1/2 cup), Granulated Sugar (1 teaspoon), and Salt (1/2 teaspoon). Add butter and toss to coat.
Using your fingertips, pastry blender, or food processor, break butter down into flour until butter is pea sized. If butter becomes too soft, just place in freezer for a few minutes and then return to working.
In a small bowl, whisk together Buttermilk (1/4 cup) and Egg (1).
Create a well in the middle of the flour/butter mixture and pour in buttermilk-eggs. With a fork, bring flour into the buttermilk-egg and stir until dough begins to form.
Empty contents out onto a clean work surface and knead dough a few times to form a shaggy ball of dough. Keep a few tablespoonfuls of buttermilk on standby just in case the dough is too dry. Add small bits if necessary.
Shape dough into a round flattened disk and wrap with plastic wrap and let rest in the fridge for at least 30 minutes to an hour.
Preheat oven to 350 degrees F (180 degrees C). Remove dough from fridge. On a lightly floured surface roll out dough into a circle 12 inches in diameter. Transfer dough to a 10-inch pie plate. Patch any holes or tears in crust with excess dough.
Tuck extra dough under itself and crimp edges. Place in freezer for 15 minutes.
Fit a large piece of parchment paper/tinfoil into frozen pie shell and fill pie shell with dried beans or pie weights. Bake for 18-20 minutes.
Remove from oven and carefully remove parchment paper-tinfoil and pie weights/dried beans, set aside to cool. With the tines of a fork, poke the bottom of the crust a few times.
Place back in oven and let bake for an additional 10 to 15 minutes until slightly golden brown. Remove and let cool. Keep oven on.
Over medium heat, cook Thick-Cut Bacon (6 slice) in a large saucepan until brown and crispy. With a slotted spoon, remove bacon from pan and let drain on a paper towel lined plate. Discard all but 2 tablespoons of bacon grease.
To the hot skillet with bacon grease, add Leek (2) and Red Chili Pepper (1). Sauté over medium - high heat until leeks have softened. If they begin to brown, decrease the temperature. Remove from heat and let cool.
In a large bowl, whisk together Egg (3). Add Milk (1 cup) and Heavy Cream (1/2 cup) and whisk until frothy. Season with Salt and Pepper (to taste).
On the bottom of the pre-baked pie crust evenly scatter half of the Shredded Cheddar Cheese (1 cup) and Swiss Cheese (1 cup). Sprinkle bacon evenly over cheese.
Evenly spread leeks and roasted red pepper over the bacon. Cover with remaining cup of cheese.
Gently pour eggs and dairy mixture over filling.
Place in preheated oven and bake until puffed and golden brown, about 35-40 minutes. It should be set and jiggle only slightly at the very center when nudged.
Remove from oven and place on wire rack and let cool at least 15 to 20 minutes before slicing. Enjoy!