Preheat the oven to 350ºF. Line the 9 x 13" baking dish with parchment paper (for the easiest cleanup ever).
In a large skillet over medium to medium-high heat, cook the sausage until crumbled & no longer pink. (I used fully cooked sausage that I diced into pieces and then browned, because it's easy.) Use a slotted spoon to transfer the sausage to a medium bowl, leaving the rendered fat in the skillet.
Add hash browns to the skillet, and cook according to their package instructions in the fat rendered from the sausage. I basically cooked mine over medium heat until they were golden and crispy.
Turn off the stove, and stir the sausage and spinach/parsley into the hash browns. Transfer to the lined 9 x 13" baking dish. Whisk the eggs, milk, and spices in a mixing bowl, and pour over top of the hash brown mixture.
Bake at 350ºF for 35 to 40 minutes, or until the eggs are set. Slice into squares & serve hot!