Pre-heat oven to 375° F.
Unfold the thawed puff pastry sheet and lay on a lightly floured surface. Roll out the pastry sheet into a rectangle, about 14 X 9 inch.
Using a knife or pastry wheel, cut puff pastry into 12 squares.
Press pastry squares into 12 muffin-pan cups. Prick the bottoms with a fork. Brush the pastries with the beaten egg.
Bake at 375° F until golden brown, approximately 10 minutes.
Remove from oven and use the back of a spoon to press down the center of the pastries to make an indentation in the cup.
Allow pastries to cool in the pan on a cooling rack for approximately 5 minutes. Remove from pan and place on waxed paper or plate.