In a large skillet over medium heat, cook the breakfast sausage until browned, breaking it apart as it cooks. Drain excess fat if necessary.
Sprinkle the flour over the cooked sausage and stir to combine. Cook for 1-2 minutes to eliminate the raw flour taste.
Gradually whisk in the milk, stirring constantly until the mixture thickens and bubbles. Add garlic powder, onion powder, black pepper, and salt. Remove from heat and set aside.
Roll out one sheet of puff pastry on a lightly floured surface to fit a 9-inch pie dish. Place the pastry in the dish, pressing it into the corners.
Pour the sausage gravy mixture into the pastry-lined pie dish. Sprinkle shredded cheddar cheese evenly over the top.
Roll out the second sheet of puff pastry and place it over the filling. Trim and crimp the edges to seal. Cut a few slits in the top to allow steam to escape. Brush the top with the beaten egg.
Bake in the preheated oven for 25-30 minutes, or until the pastry is golden brown and puffed.
Allow to cool for 5-10 minutes before slicing and serving.
Notes
For a spicier version, add crushed red pepper flakes or use spicy sausage.
You can substitute the cheddar cheese with pepper jack or mozzarella for a different flavor profile.