- 1 frozen puff pastry sheet, thawed (half of 17 1/4-ounce package)
- 1 egg beaten with 1 tablespoon water (glaze)
- Sugar
- 3 ounces bittersweet (not unsweetened) or semisweet chocolate, chopped
- 1 tablespoon plus 1/4 cup currant jelly
- 2 tablespoons plus 1/4 cup sour cream
- 3/4 cup raspberries
- 3/4 cup blueberries
- crème de cassis liqueur (optional)
- Preheat oven to 350°F. Roll out pastry on floured surface to 14×11-inch rectangle. Trim two 1-inch-wide strips off each edge (for a total of 8 strips) and reserve. Transfer pastry rectangle to ungreased baking sheet. Pierce rectangle all over with fork. Brush with glaze. Arrange 1 pastry strip atop each edge of rectangle, trimming to join strips at corners. Brush with glaze. Top each edge with remaining pastry strips, covering corner seams and trimming to square off. Brush with glaze. Sprinkle with sugar. Bake 5 minutes. Pierce pastry rectangle (not sides) all over with fork. Continue baking until golden, about 20 minutes longer. Cool on rack.
- Melt chocolate in top of double broiler over simmering water, stirring until smooth. Add 1 tablespoon jelly; stir until melted. Add 2 tablespoons sour cream; mix until smooth. Spread in crust.
- Melt remaining 1/4 cup jelly in small saucepan over low heat, stirring often. Combine berries in bowl. Add melted jelly; stir to coat. Immediately spoon berries atop soft chocolate in crust, covering chocolate completely. Chill just until set, about 1 hour. Let stand at room temperature. (Can be made 6 hours ahead.)
- Combine 1/4 cup sour cream and crème de cassis. Serve with tart.