1. Mound chilled filling along the centre of of smaller pastry rectangle, leaving a 3/4-in. border around the edges. Lay larger piece of pastry on top of filling, pressing edges together.
2. Trim and straighten edges with a paring knife. Press the tines of a fork around the edges to crimp.
3. Beat egg yolk with 1 tbsp water. Brush egg wash all over pastry. Cut 4 slits on the top of the pastry.
4. Gather remaining dough and roll out to 1/4-in. thick. Use cookie cutters or a paring knife to cut out different shapes and designs. Place on top of pastry, then brush with remaining egg wash.