Chocolate, Nut and Caramel Shortbread Tart

Ingredients
14 oz shortbread biscuits, halved
1 egg, lightly beaten
6 oz dark brown sugar
1 1/2 cups pouring cream
3 1/2 oz butter, chopped
1 tsp vanilla extract
3 oz slivered pistachios

3 oz slivered almonds

3 oz chopped walnuts, lightly roasted
7 oz dark chocolate (60 percent cocoa solids), finely chopped
Dutch-process cocoa, for dusting

Directions:
Preheat oven to 375 F. Process biscuits in a food processor until fine crimbs form. With mortor running, add egg and process until mixture is evenly damp. Using your hands and the base of a glass, press crumb mixture evenly and firmly over base and sides of a greased 10 inch round loose-based fluted tart tin. Bake in oven for 12-14 minutes or until tart case is dry. Set aside to cool.
Place sugar, 1/2 cup of cream, butter and banilla ina saucepan. Stir over medium heat until combined, then simmer for 8 minutes. Stir in nuts, then spoon into tart case. Set aside to cool.
Place remaining cream in a small saucepan and bring almost to the boil over medium heat. Remove from heat, add chocolate, and stir until chocolate melts and mixture us smooth abd cimbined. Spoon over caramel layer in tart case, level with a spatula, then refrigerate for 2 hours until set. Dust tart with cocoa and cut into then slices to serve. This tart will keep in the refrigerator for up to 3 days.