Chocolate Orange Hazelnut Tart inspired by Hotel Chocolat

g/ 1/3 cup butter (chilled and cubed)

g/1 1/4 cup flour

g1/3 cup finely ground hazelnuts

cocoa

g/1/3 cup brown sugar

ml/3/4 cup double cream/whipping cream

g/8oz good quality dark chocolate (chopped (not chocolate chips))

g/1/4 cup mascarpone

chocolate hazelnut spread like Nutella

Cointreau or orange flavouring

ml/1 cup double cream/whipping cream

g/1/4 cup mascarpone

chocolate hazelnut spread

chopped hazelnuts for decoration (optional)