Fry the minced meat and onions. Season with salt, pepper and hot paprika. Add paprika and leek and fry briefly. Add tomato paste, mustard and a little water. Mix well and let cool.
Roll up the puff pastry, spread the really cold (!) Minced meat mixture on top (leave a wide margin) and top with flakes of cream cheese (Philadelphia or inexpensive). Let it really cool down, otherwise the puff pastry may dissolve.
Brush the puff pastry with the beaten egg, roll up or fold up the edges - also brush the edges with egg white. Brush the outside of the roll with the egg.
The whole thing comes in the oven at 180 degrees for 45 minutes - that`s how long the puff pastry takes. Otherwise it`s sticky.