In a skillet add diced onions and ground beef. Cook until no longer pink.
To the skillet add salt, garlic powder, onion powder, paprika, ketchup, and mustard. Mix to combine. Set aside for later.
In a small bowl add egg and 2 tablespoon of water. Mix to combine.
Gently roll out each sheet of puff pastry and cut each sheet into 3 rectangles.
On half of each rectangle add about ¼ cup of the meat mixture and 2 tablespoon of shredded cheese. Keeping about ¼" boarder. Brush the perimeter of the puff pastry with the egg mixture.
Fold the other half of the puff pastry over top to create a sandwich, then press a fork to seal the edges all the way around.
Place the pizza pockets onto a baking dish and brush with egg mixture. Sprinkle with sesame seeds if using.
Bake in the oven for 15-17 minutes or until golden brown.
Notes
Don't overfill them. I know it's tempting to pile on the meat, but too much filling makes it really hard to seal the edges and they'll pop open in the oven. Stick to about ¼ cup of meat per pocket.Let the filling cool before adding it to the pastry. Hot filling on cold pastry can make it soggy. Just give it 5-10 minutes off the heat.Press that fork seal firmly. Go around all three sides twice if you need to. A good seal keeps everything inside where it belongs.Don't skip the egg wash on top. That's what gives you that beautiful bakery-style golden color. It makes such a difference!