Using a wooden spoon, mix 14 tablespoons butter in a bowl until light and fluffy. Grind nuts and sugar in a food processor, and mix into the butter. Beat in egg. Add both flours, and blend until just combined. Gather dough into a ball, and flatten into a disk. Wrap in plastic; chill 2 hours.
Roll out dough to a 15 inch circle between two sheets of plastic. Remove top sheet of plastic, and transfer dough to an 11 inch tart pan with a removable bottom. Press into pan, and trim edges. Place in the freezer for 15 minutes. Line dough with foil, and fill foil with dried beans (serves as a weight to help the crust keep it's shape).
Bake at 350 degrees F (175 degrees C) for 15 minutes. Remove foil and beans. Bake until crust is golden, about 20 minutes. Cool.
Combine sugar and water in a heavy saucepan. Cook over medium heat, stirring until mixture is a deep amber color, about 15 minutes. Brush down sides of pan with a wet brush, and swirl occasionally. Remove from heat. Gradually stir in 1 1/4 cups heavy cream. Add 1/4 cup butter, and stir until melted. Pour filling into crust.
Bake at 350 degrees F (175 degrees C) until filling bubbles and thickens, about 30 minutes. Filling will be wobbly. Cool. Chill until set, about 1 hour.
In a heavy small saucepan, combine 3/4 cup heavy cream, chocolate, 3 tablespoons butter, and corn syrup. Cook over low heat, stirring until smooth. Pour over chilled filling. Chill tart until firm, about 1 hour. Let stand 30 minutes at room temperature before serving.
Tips & Tricks
Make this simple recipe for festive caramel popcorn.