Preheat your oven to 375°F (190°C) to ensure even baking and a golden crust.
If using store-bought crust, fit it into your pie dish as per package instructions. For homemade crust, roll out and place in the dish, trimming excess. Optionally, blind bake for 10 minutes.
In a large mixing bowl, whisk together 6 large eggs, 2 cups heavy cream, 1 cup whole milk, 1 teaspoon salt, and 1 teaspoon ground pepper until smooth and frothy.
Add your favorite fillings like sautéed spinach, diced tomatoes, cooked bacon, or cheeses. Pour the egg mixture evenly over the fillings.
Bake the quiche in the preheated oven for 35-40 minutes, until the filling is set and the top is lightly golden. A knife inserted in the center should come out clean.
Remove from oven and cool for about 10 minutes before slicing. Serve warm or at room temperature.