Preheat your oven to 400°F (200°C).

Grease a 9-inch springform pan or pie dish. Line it with parchment paper cut to size, including the sides. Grease it again, lightly.

In a large mixing bowl, combine the thawed hash browns, melted butter, egg, salt, and pepper.

Press the hash brown mixture evenly into the bottom and up the sides of the pan to form a crust.

Bake the crust in the preheated oven for 20-25 minutes, or until it becomes golden brown and slightly crispy.

Meanwhile, whisk together the eggs, milk, salt, pepper, and nutmeg, if desired in a bowl. Set aside.

In a skillet, sauté the diced bell peppers, onion, and minced garlic until they soften, about 6-8 minutes. Add the baby spinach and cook until it wilts, then remove from heat.

Remove the quiche from the oven. Sprinkle half of the shredded Gruyere cheese evenly over the baked hash brown crust.

Add the crumbled bacon (or ham) evenly over the cheese. Add the sauteed peppers and onions.

Pour the egg mixture over the vegetables and bacon.

Sprinkle the remaining Gruyere cheese on top.

Reduce the oven temperature to 350°F (175°C).

Place the springform pan on a baking sheet (to catch any potential spills) and bake the quiche for 35-40 minutes, or until the center is set and the top is golden brown. You can check for doneness by inserting a knife or toothpick into the center – it should come out clean.

Allow the quiche to cool before removing it from the pan.

Garnish with fresh herbs like parsley or chives, sour cream, salsa, avocado slices, crumbled feta if desired.