For the crust: process flour, sugar, and chocolate in food processor. Add rest of ingredients. Press into a lightly greased 11-inch tart pan with removable bottom. Bake until firm, about 15 to 20 minutes.
Lower the oven to 350 degrees F.
For the Filling: pour the hot butter over the chocolate and stir until melted and smooth. In a mixer, beat the sugar and eggs together. Add the orange liqueur, flour, and zest. Add chocolate butter mixture. Pour into tart shell. Bake for 35 minutes, or until cooked through, but not overcooked. When cooled, spread with topping.
For the topping: pour the boiling cream over the chocolate. Stir until smooth. Spread over cooled tart. Refrigerate until firm. Serve slightly warmed with whipped cream and berries.