Thaw the frozen hash browns and squeeze out any excess moisture using a clean kitchen towel. In a mixing bowl, combine the hash browns with half of the shredded cheddar, salt, and pepper. Grease a 9-inch springform pan and press the hash brown mixture into the bottom and up the sides to form a crust. Freeze the crust for at least 1 hour to help it hold its shape.

Preheat your oven to 425°F (220°C). Once the oven is heated, bake the hash brown crust for 15 minutes until it turns golden brown and slightly firm to the touch.

Melt the unsalted butter in a skillet over medium heat. Add the finely diced onions and cook for 10–15 minutes, stirring frequently, until they are golden and caramelized. Season lightly with salt and pepper.

In a large mixing bowl, whisk together the six large eggs and half a cup of heavy cream until frothy and fully combined. Gently fold in the remaining shredded cheddar cheese, the caramelized onions, crumbled bacon, and additional salt and pepper.

Reduce the oven temperature to 375°F (190°C). Carefully pour the egg mixture into the pre-baked hash brown crust. Bake for 25–30 minutes, or until the filling is set and the top is lightly golden.

Remove the quiche from the oven, and carefully run a knife around the edges to loosen it. Return the quiche to the oven without the sides of the springform pan for an additional 10–15 minutes.

Let the quiche cool for at least 10 minutes before slicing. Garnish with freshly chopped chives and serve warm.