The blueberry-raspberry tart can be baked up to 6 hours ahead and kept at room temperature.
Variation To make 12 individual tarts, increase the pastry recipe by half. Divide the pastry into 12 equal portions and pat into disks. Refrigerate for at least 30 minutes or overnight. Roll out into 7-inch rounds, about 1/8 inch thick. Spread 1/2 cup of the berry filling on each round, leaving a 1-inch border, then proceed through the rest of Step 3.