On a floured surface, roll the dough into a 25 x 38-cm (10 x 15-inch) rectangle. Arrange the cheese pieces along the edge of the shorter side. Cut the dough between the pieces, leaving a 1-cm (1/2-inch) border around each. Brush the border with egg white. Cut the remaining dough into 4 squares and use to cover the cheese pieces. Trim any excess dough, leaving a 2-cm (1-inch) edge. Fold 1 cm (1/2 inch) of the edge back toward the cheese. Using the tines of a fork, press the edge around each piece to seal. Make a pea-sized hole in the dough above each piece of cheese. Transfer to the parchment lined baking sheet. Beat the egg yolk with the remaining white and brush the dough with the mixture. Freeze for 20 minutes or refrigerate for 45 minutes.
