Preparation:

 Take the pieces out of the freezer in order to restore softness.

arrange the puff pastry in a tray greased with little butter.

Then put the tray on the middlegrid of a moderately hot oven until the pieces are of golden color.

Prepare the béchamel cream (butter, flour, milk), cutt a pieces of fricassee chicken.

Take the tray out of the oven and put a huff of  the béchamel cream on the dough, arrange the fricassee chicken on, and 

put the last béchamel cream again.

cut a pieces of mozzarella on the tray, put it again in the hot oven.