Step #1 Thaw the sheets of puff pastry according to package instructions.
Step #2 Cut into desired shapes & size.
Step #3 (My puff pastry usually comes in six small sheets which I cut into eight triangles each, but you could also make them bigger or use cookie cutters to make fancy shapes.
Step #4 ).
Step #5 Top each with some pizza sauce & tuna & finish with a slice of mozzarella.
Step #6 Bake in a pre-heated oven at 350°F/180°C/Gas 4 for approximately 20-25 mins.
Step #7 Can be served straight away or served cold.