1. Preheat oven to 350°F (175°C). In a mixing bowl, combine flour and sugar. Cut in butter until mixture resembles coarse crumbs. Add egg yolk and cold water, mix until dough forms. Press dough into tart pan. Bake for 15 minutes. Let cool.
2. In a saucepan, melt sugar over medium heat until it turns amber. Add butter and stir until melted. Slowly add cream and vanilla, stirring constantly. Pour caramel into tart crust. Let cool.
3. Heat cream for ganache until simmering. Pour over chopped chocolate and let sit for 5 minutes. Stir until smooth. Pour ganache over caramel layer. Chill tart in refrigerator for at least 1 hour before serving.