Mix sour cream, cream cheese and dip mix together until well blended. Stir in Parmesan cheese. Add crabmeat; toss gently.
Roll out the defrosted puff pastry dough on a floured surface and cut it into 12 squares if you're planning on using mini muffin tins. I started by cutting my first sheet into 3 long strips and then into 4 smaller squares. Depending on how much filling you use in each puff, you might need to use the second sheet of puff pastry.
Place a square of dough into the muffin tin, push it against the sides and leave the corners draped over the edge - then spoon some of the crab mixture into the center and fold the corners of the dough over the filling and pinch them together in the center.
Once you've used up all of the filling, beat the egg with a tbsp of water and brush the tops of the puff pastry with the egg wash and bake at 400°F until the pastry is golden and puffed - approximately 20 minutes.
Run a sharp knife around the edges of the pan to loosen and turn them out onto a rack to cool a bit before serving.
*If you're planning on serving these at a later date, do not brush with egg wash and just freeze them in the muffin tins wrapped tightly in plastic wrap and then aluminum foil. If you want to remove them from the pans, freeze them first and then pop them out once frozen and store them in plastic freezer bags. You can bake these frozen, just don't forget to brush them with the egg wash before baking them and you might need to add a few minutes to the bake time. Alternatively, you can totally defrost them and bake as originally directed.