Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or butter.

In a skillet over medium heat, cook the breakfast sausage until browned and crumbly, breaking it apart with a spatula. Remove the sausage from the skillet and set aside, leaving the grease in the pan.

To make the sausage gravy, add the flour to the skillet with the sausage grease and whisk until combined, forming a roux. Slowly pour in the 2 cups of whole milk, whisking constantly to avoid lumps. Cook the gravy over medium heat until thickened, about 5-7 minutes. Season with black pepper, salt, and garlic powder. Remove from heat and set aside.

In a mixing bowl, whisk together the eggs and 1/4 cup milk. Heat 1 tablespoon butter in a separate skillet over medium heat. Pour the egg mixture into the skillet and scramble the eggs until just set, about 3-4 minutes. Remove from heat.

Lay out each tortilla and fill with a scoop of scrambled eggs, a sprinkle of cheddar cheese, and a portion of the cooked sausage. Roll the tortillas tightly and place them seam-side down in the prepared baking dish.

Pour the sausage gravy evenly over the rolled tortillas, ensuring they are fully covered. Sprinkle the Monterey Jack cheese on top of the gravy.

Bake the enchiladas in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.

Remove the enchiladas from the oven and let cool for 5 minutes. Garnish with fresh parsley, if desired, and serve warm.