Start by squeezing excess moisture from the thawed hash browns to prevent a soggy crust. In a mixing bowl, combine the drained hash browns with shredded white cheddar, salt, and pepper. Mix well until evenly coated, then transfer into a greased 9-inch springform pan, pressing it firmly into the bottom and up the sides.

Once the hash brown mixture is shaped into a crust, place the springform pan in the freezer for at least 1 hour.

Preheat your oven to 425°F (220°C). After the crust has chilled, bake it for 15 minutes, or until lightly set and golden at the edges.

While the crust is cooling, melt unsalted butter in a skillet over medium heat. Add finely chopped onions and sauté for about 10-15 minutes until caramelized.

In a large bowl, whisk together the eggs and heavy cream until light and fluffy. Stir in the caramelized onions, shredded white cheddar, and crispy bacon.

Reduce the oven temperature to 375°F (190°C). Carefully pour the filling into the pre-baked hash brown crust, leaving a small gap at the top. Bake for 25-30 minutes until just set and lightly puffed.

Remove the quiche from the oven and let it cool for 10 minutes before slicing.