Instructions: For crust:
Mix flour and sugar in processor. Add butter; cut in using on/off turns until mixture resembles coarse meal. Add yolk, cream and vanilla; blend using on/off turns until dough begins to clump together. Gather into ball; flatten into disk. Wrap in plastic; chill 30 minutes.

Preheat oven to 350F. Roll out dough on lightly floured surface to 11-inch round. Transfer dough to 9-inch-diameter tart pan with removable bottom. Trim edges. Freeze crust 15 minutes. Line with foil. Fill with dried beans or pie weights. Bake until sides are set, about 10 minutes. Remove foil and beans; bake crust until golden, piercing with toothpick if crust bubbles, about 20 minutes more. Cool completely on rack.

For filling:
Combine 1/3 cup sugar, 3 tablespoons cream and butter in heavy small saucepan. Stir over medium heat until sugar dissolves and butter melts. Pour into medium bowl and cool to room temperature. Add cream cheese, peanut butter and vanilla to brown sugar mixture. Using electric mixer, beat until smooth. Whisk remaining 1/4 cup cream with remaining 2 tablespoons brown sugar in small bowl to stiff peaks; fold into peanut butter mixture. Spoon filling into tart shell; smooth top. Refrigerate until firm, about 1 hour.

For topping:
Stir first 4 ingredients and 2 tablespoons cream in heavy medium saucepan over low heat until sugar dissolves. Increase heat to medium; stir slowly until clip-on candy thermometer registers 222F, about 8 minutes. Remove from heat. Add 2 tablespoons cream and nuts.

Let stand just until cool, about 20 minutes. Spoon over filling.

Chill until set, at least 2 hours or overnight.

Remove pan sides from tart. Transfer tart to platter. Sprinkle white chocolate around edges, if desired.

Serves 8.

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