Stir together 1/3 cup flour and 3/4 cup sugar; whisk in eggs.
Cook milk in a heavy saucepan over medium heat until hot. Gradually whisk about one-fourth of hot milk into egg mixture; add to remaining hot milk, whisking constantly.
Cook over medium-high heat, whisking constantly, 5 to 6 minutes or until thickened. Remove from heat; stir in vanilla and 1 cup coconut. Cover and chill 3 hours.
Bake remaining 1/2 cup coconut in a shallow pan at 350°, stirring occasionally, 5 to 6 minutes or until toasted; set aside.
Pulse 2 1/2 cups flour and butter in a food processor until crumbly. Add 2 tablespoons water, and pulse 30 seconds or until dough forms a ball. Turn out onto a lightly floured surface; knead in nuts.
Divide dough into 12 equal portions; press each portion into a(3- to 4-inch) tart pan. Prick bottoms with a fork, and place on a 15- x 10-inch jellyroll pan. Cover and freeze 30 minutes.
Bake on jellyroll pan at 375° for 15 to 20 minutes or until golden. Cool in tart pans 5 minutes; remove from pans, and cool completely on a wire rack.
Spoon coconut custard mixture into tart shells.
Beat whipping cream and 3 tablespoons sugar at high speed with an electric mixer until soft peaks form; dollop or pipe onto tarts. Sprinkle with toasted coconut; chill.