In a large skillet over medium heat, brown the breakfast sausage until fully cooked, about 5-7 minutes. Stir in the all-purpose flour and cook for 2 minutes. Gradually whisk in the whole milk, then reduce the heat to medium-low, allowing the gravy to thicken for about 4-5 minutes. Season with seasoned salt and black pepper to taste, then set aside.

In a separate non-stick skillet, crack and scramble the large eggs over medium heat, stirring frequently until just set, about 3-4 minutes. Adjust doneness to your preference and set aside.

In a mixing bowl, whisk together the all-purpose flour and salt. Cut in the vegetable shortening and cold butter until the mixture resembles coarse crumbs. Mix in a beaten egg, white vinegar, and cold water as needed to form a soft dough, then wrap and refrigerate for 30 minutes.

Roll out half of the chilled dough to about 1/8-inch thickness and cut into rectangles measuring 3x4 inches, aiming for a total of 8 rectangles. Preheat your oven to 375°F while preparing.

Line a baking sheet with parchment paper, place four rectangles on it, brush edges with egg wash, and fill with scrambled eggs and sausage gravy. Lay remaining rectangles on top, sealing edges.

Brush tops with egg wash, sprinkle with cheese and optional seasonings, and bake at 375°F for about 25 minutes, or until golden brown.

Let cool on baking sheet for about 5 minutes before serving warm.