Preheat the oven to 325°F. Make the crust: In a food processor, grind the nuts and brown sugar until fine. Slowly add the melted butter and mix until the dough sticks together when pinched. Press the dough evenly into the bottom and up the sides of a 10-inch fluted tart pan with a removable bottom. Parbake for 20 minutes or until lightly golden. Let cool completely before filling.
Make the filling: In a bowl, mix together the eggs, brown sugar, mashed sweet potato, melted butter, cream, vanilla, cinnamon, salt, nutmeg, and ginger. Pour the filling into the pie shell and bake until the filling is just set, slightly browned around the edges, and no longer looks wet, 50 to 60 minutes. Let cool completely on a wire rack before removing from the pan. Garnish with candied ginger, slice, and serve.