Preheat your oven to 375°F (190°C). In a mixing bowl, blend the softened butter and self-rising flour until it resembles coarse crumbs. Gradually add 2 to 3 tablespoons of cold water and mix until a dough forms. Press the dough evenly into the bottom and up the sides of your 9-inch pie dish.
In a skillet over medium heat, cook the breakfast sausage until browned and fully cooked, about 7-10 minutes. Break the sausage into small pieces as it cooks. Once done, drain excess grease and set aside.
In a large mixing bowl, whisk together the eggs, heavy cream, milk, kosher salt, and ground black pepper until well combined. Stir in the cooked sausage and grated cheddar cheese until evenly distributed.
Pour the sausage and cheese filling into the prepared crust. Make sure it's evenly spread for consistent cooking.
Place the quiche in the preheated oven and bake for 35-40 minutes, or until the quiche is set and the top is golden brown. A knife inserted in the center should come out clean.
Once baked, remove the quiche from the oven and let it cool for about 10 minutes before slicing. This resting time helps the filling set further, making it easier to serve.
