Served plain, sand tarts are like cookies; invert them on the plate so the impression of the mold shows. If you serve the pudgy little pastries right side up, spoon a small puff of sweetened whipped cream in the slightly depressed center and top with several fresh berries -strawberries, raspberries, or blueberries - or fresh currants. You can make the dough (steps 1 and 2) up to 3 days ahead; wrap airtight and chill. Bring to room temperature before continuing. You can make the tarts up to 3 days ahead; wrap airtight when cool and let stand at room temperature. Freeze to store longer.