Preheat your oven to 375°F and prepare your workspace by placing the unbaked pie crust in a 9-inch quiche dish. Press it gently into all corners and up the sides, then prick the bottom with a fork to prevent puffing during baking. This simple step ensures an evenly cooked crust.

In a large mixing bowl, whisk together all nine eggs, the heavy cream, and whole milk until the mixture is completely smooth and well combined. Add your salt, black pepper, and nutmeg to the custard base, stirring thoroughly to distribute spices evenly throughout.

Heat the 2 tbsp of butter in a skillet over medium heat, then sauté your diced onion for 2-3 minutes until softened and fragrant. Add the bell peppers and mushrooms, cooking for another 3-4 minutes until the vegetables release their moisture and begin to soften slightly.

Layer your sautéed vegetables and diced smoked turkey evenly across the unbaked pie crust. Sprinkle the shredded cheddar cheese over the filling, then slowly pour your prepared egg custard mixture over everything, ensuring the liquid reaches about three-quarters up the sides.

Bake your cozy quiche brunch recipe in the preheated 375°F oven for 40-45 minutes until the top turns golden brown and a knife inserted near the center comes out clean. The filling should jiggle only slightly in the very center when gently shaken; this indicates perfect doneness.

Remove the quiche from the oven and let it rest on the counter for 5-10 minutes before slicing. This resting period allows the custard to set completely and makes serving much easier without disrupting the presentation.