Preheat oven to 200°C.
Roll pastry to fit a 2-quart oval baking dish. In a large bowl, combine peaches and blueberries. Mix in flour, sugar, nutmeg, vanilla and butter cubes. Pour into the baking dish and cover with pastry. Using a fork, cut off excess dough and create a decorative edge by pressing tines along edge of pan and pushing down. With a paring knife, cut 3 slices on top of the pastry to vent. Brush on egg wash and dust with sugar. Bake until golden brown on top and edges are bubbling, about 45 to 50 minutes.