Marbleized Mocha Tart

PreparationFor crust: Blend flour, powdered sugar and salt in processor 5 seconds. Add butter and cut in using on/off turns until mixture resembles coarse meal. Mix in yolk and enough water to form moist clumps. Knead dough briefly on work surface to combine; flatten into disk. Wrap in plastic and refrigerate until firm, at least 2 hours and up to 1 day. Preheat oven to 375°F. Roll out dough on lightly floured surface to 16-inch round (scant 1/8 inch thick). Transfer dough to 11-inch-diameter tart pan with removable bottom. Press dough into pan; trim excess. Freeze crust 15 minutes. Place tart pan on baking sheet. Bake crust 10 minutes; pierce with toothpick if crust bubbles. Continue to bake until crust is pale golden, about 12 minutes. Transfer to rack; cool crust completely. For Mocha Ganache: Stir chocolate, cream and espresso powder in heavy medium saucepan over low heat just until chocolate melts and mixture is smooth (mixture will be warm, not hot). Pour mocha ganache into prepared crust. For White Chocolate Ganache: Stir white chocolate and cream in heavy small saucepan over very low heat just until chocolate melts and mixture is smooth. Drizzle over mocha ganache. Using tip of small knife or toothpick, swirl fillings together to marbleize. Refrigerate tart until filling is cold and firm, at least 3 hours. (Can be prepared 2 days ahead. Cover and keep refrigerated.) Push pan bottom up to free tart from pan. Cut tart into wedges and serve.

PreparationFor crust: Blend flour, powdered sugar and salt in processor 5 seconds. Add butter and cut in using on/off turns until mixture resembles coarse meal. Mix in yolk and enough water to form moist clumps. Knead dough briefly on work surface to combine; flatten into disk. Wrap in plastic and refrigerate until firm, at least 2 hours and up to 1 day. Preheat oven to 375°F. Roll out dough on lightly floured surface to 16-inch round (scant 1/8 inch thick). Transfer dough to 11-inch-diameter tart pan with removable bottom. Press dough into pan; trim excess. Freeze crust 15 minutes. Place tart pan on baking sheet. Bake crust 10 minutes; pierce with toothpick if crust bubbles. Continue to bake until crust is pale golden, about 12 minutes. Transfer to rack; cool crust completely. For Mocha Ganache: Stir chocolate, cream and espresso powder in heavy medium saucepan over low heat just until chocolate melts and mixture is smooth (mixture will be warm, not hot). Pour mocha ganache into prepared crust. For White Chocolate Ganache: Stir white chocolate and cream in heavy small saucepan over very low heat just until chocolate melts and mixture is smooth. Drizzle over mocha ganache. Using tip of small knife or toothpick, swirl fillings together to marbleize. Refrigerate tart until filling is cold and firm, at least 3 hours. (Can be prepared 2 days ahead. Cover and keep refrigerated.) Push pan bottom up to free tart from pan. Cut tart into wedges and serve.