In a large mixing bowl, whisk together flour, salt, sugar, and baking powder. Cut in butter until mixture resembles coarse crumbs. Combine milk and egg in a separate bowl, then mix into dry ingredients to form a soft dough.

On a floured surface, roll out the dough to 1/4-inch thickness. Cut the dough into 6 to 8 rectangles, 4x6 inches each, and place on a parchment-lined baking sheet.

In a medium bowl, mix sausage, scrambled eggs, cheese, and Dijon mustard. Ensure the mixture is well combined and not overly runny.

Take a rectangle of dough, add a spoonful of filling on one half, fold the other half over, and press down to seal. Crimp the edges with a fork.

Whisk together an egg and water for an egg wash. Brush the tops of each hot pocket with the mixture.

Preheat oven to 375°F (190°C). Bake hot pockets for 20 to 25 minutes until golden brown.

Remove from oven and cool on a wire rack for 5 minutes before serving.