PreparationFOR CRUST: Blend first 4 ingredients in processor until finely chopped. Add butter; cut in using on/off turns until mixture resembles coarse meal. Add milk and vanilla; process until moist clumps form. Using plastic wrap as aid, press dough over bottom and up sides of 11-inch-diameter tart pan with removable bottom. Freeze 30 minutes. Preheat oven to 350°F. Bake crust until just set and beginning to brown around edges, about 8 minutes. Transfer pan to rack and cool crust completely. Maintain oven temperature. FOR FILLING: Stir butter and chocolates in medium saucepan over low heat until melted. Cool slightly. Beat sugar, eggs, vanilla and salt in medium bowl until fluffy, about 4 minutes. Whisk in chocolate mixture. Mix in flour and nuts. Pour batter into crust. Bake until filling puffs around edges and tester inserted into center comes out with moist crumbs attached, about 40 minutes. Transfer to rack and cool completely. FOR TOPPING: Stir semisweet chocolate, butter and oil in small saucepan over low heat until melted. Spread over tart. Chill until set, about 15 minutes. Stir white chocolate in top of double boiler over simmering water until melted. Drizzle atop tart. Chill until set, about 10 minutes. (Can be made 1 day ahead. Cover and chill.) Serve at room temperature.
PreparationFOR CRUST: Blend first 4 ingredients in processor until finely chopped. Add butter; cut in using on/off turns until mixture resembles coarse meal. Add milk and vanilla; process until moist clumps form. Using plastic wrap as aid, press dough over bottom and up sides of 11-inch-diameter tart pan with removable bottom. Freeze 30 minutes. Preheat oven to 350°F. Bake crust until just set and beginning to brown around edges, about 8 minutes. Transfer pan to rack and cool crust completely. Maintain oven temperature. FOR FILLING: Stir butter and chocolates in medium saucepan over low heat until melted. Cool slightly. Beat sugar, eggs, vanilla and salt in medium bowl until fluffy, about 4 minutes. Whisk in chocolate mixture. Mix in flour and nuts. Pour batter into crust. Bake until filling puffs around edges and tester inserted into center comes out with moist crumbs attached, about 40 minutes. Transfer to rack and cool completely. FOR TOPPING: Stir semisweet chocolate, butter and oil in small saucepan over low heat until melted. Spread over tart. Chill until set, about 15 minutes. Stir white chocolate in top of double boiler over simmering water until melted. Drizzle atop tart. Chill until set, about 10 minutes. (Can be made 1 day ahead. Cover and chill.) Serve at room temperature.