Preheat oven to 425 degrees F. Line a baking sheet with parchment paper and place the bacon in an even layer on the baking sheet. Bake until crisp, turning once halfway through, about 20 minutes.
Remove the baking sheet from the oven and transfer the bacon to a towel-lined plate. When cool enough to handle, roughly chop the bacon and set aside. Reserve 1/2 cup bacon for garnish.
In a large bowl, toss to combine the hash brown potatoes, parmesan cheese, 1/3 cup grated cheddar cheese, salt and pepper.
Spread the hash browns in an even layer on the parchment paper with the bacon grease. Bake until the hash browns are lightly crisp, about 20 minutes.
In a large bowl, whisk to combine the eggs, milk, salt and pepper. Fold in the chopped bacon, 1 cup shredded cheddar cheese and spinach. Pour into the hash brown crust and spread to make even. Top with 2/3 cup shredded cheddar cheese and place in oven. Bake until eggs are puffed and cooked through, about 25-30 minutes.
Top with reserved chopped bacon, scallions and drizzle with hot sauce to serve.