Crab rangoon filling: add cream cheese, crab, and the thinly sliced whites of scallions to a large bowl and stir to combine well. This is your crab rangoon filling, and you can store it in the refrigerator until time to use or for no more than 4 or 5 days. 

Puff pocket filling: lay out 1 sheet at a time and cut the sheet twice to form 3 equal-sized rectangles. Then I cut each rectangle in half, forming 6 equally sized sheets. 

Using a fork, dock or poke each small rectangle many times, covering the surface of the dough. This helps keep the pastry from puffing up too much. It will still puff up, but it will be better if you dock it thoroughly. 

Whisk 1 large egg in a bowl with 1 tablespoon of water. This will be your egg wash, which will be "glue" to hold the pastry pieces together, and it will also be painted on the top of each puff pocket to help toppings stick and to create a nice brown and slightly shiny exterior. 

Filling and closing the puff pockets: add a tablespoon or 1.5 tablespoons of crab rangoon filling right in the middle of a dough rectangle. Mash the filling down a little, but don't let it get too close to the edges of the pastry. With a pastry brush or spoon, paint some egg wash all around the outside edges of the pastry. 

Place a second dough rectangle on top of the dough and filling, and then using a fork, go all around the edge of the pastry pocket and mash the two dough rectangles together. 

Paint the top of each puff pocket with more egg wash. Then, with a fork, poke some air holes in the top of the pocket (where the filling is) and then top each egg-washed pastry with sesame seeds or black pepper and parmesan (or a combination of all) to create a more interesting top. 

Place each formed puff pocket on a parchment-lined sheet pan. Preheat the oven to 425°F (220°C), and when they are all ready, you can bake them for 20 minutes, turning the pans 180 degrees at the halfway point so that they bake evenly.