In a large skillet over medium heat, cook the breakfast sausage until browned and crumbled, about 5-7 minutes. Sprinkle flour and stir until absorbed. Gradually whisk in milk, reduce heat to low, and stir continuously until thickened. Season and set aside to cool.

In a separate bowl, crack and whisk the large eggs together. Scramble in a non-stick skillet over medium heat for about 3-5 minutes. Remove from heat and let cool slightly.

Preheat the oven to 375°F (190°C). Whisk together flour and salt in a large mixing bowl. Cut in shortening and butter until it resembles coarse crumbs. In a smaller bowl, mix egg, vinegar, and cold water, then gradually add to dry ingredients until a dough forms.

Roll out the dough on a floured surface to about ⅛-inch thickness and cut into 3x4 inch rectangles. Gather scraps, reroll, and cut more rectangles.

Place half the dough rectangles on a lined baking sheet. Brush edges with egg wash. Layer scrambled eggs and sausage gravy on each piece, top with another rectangle, sealing edges securely.

Brush the tops with egg wash and sprinkle cheese and seasoning if desired. Bake in preheated oven for about 25 minutes or until golden brown.

After baking, allow to cool on the baking sheet for about 5 minutes before serving.