Blackberry Custard Torte

1 cup all-purpose flour
1/2 cup sugar
1-1/2 teaspoons baking powder
1/2 cup cold butter
1 egg

3 egg yolks
2 cups (16 ounces) sour cream
1/2 cup sugar
1/4 teaspoon vanilla extract
4 cups fresh or frozen blackberries, drained, divided
Whipped cream

In a small bowl, combine the flour, sugar and baking powder; cut in butter until crumbly. Stir in egg until dough forms a ball. Press onto the bottom and 2 in. up the sides of an ungreased 9-in. springform pan.

For filling, beat the egg yolks, sour cream, sugar and vanilla in another small bowl just until combined. Sprinkle 2 cups blackberries over crust. Carefully pour sour cream mixture over berries. Place pan on a baking sheet.

Bake at 325° for 1-1/2 hours or until center is almost set. Cool on a wire rack (center will fall). Remove sides of pan. Top with whipped cream and remaining blackberries. Refrigerate any leftovers. Makes 12-14 servings.