Make the crust: In a bowl, combine the crust ingredients and mix thoroughly (graham cracker crumbs, ginger, brown sugar, salt, and butter). Press the mixture into a 9x9-inch (2.5 quart or 23cmx23cm) baking dish.
Stovetop: In a saucepan, combine the cream and chocolate. Cook over low heat, stirring frequently, until the chocolate is melted and completely combined with the cream.
Microwave: In a microwave safe bowl, combine the cream and chocolate. Microwave for 45 seconds. Stir and mash the chocolate chips, and then continue melting in 15 second intervals, stirring and mashing in between, until chocolate is completely melted and smooth.
Pour the mixture over the crust; tilt and gently shake the pan to spread the mixture evenly. Set aside to cool for at least 10 minutes before adding the sweet potato filling.
Make the sweet potato filling: In a bowl, combine the sweet potato filling ingredients and mix well (sweet potato puree, egg, salt, cinnamon, clove, brown sugar, and half & half). Gently pour the sweet potato filling over the chocolate layer.
Slice with a clean knife into even squares, wiping the knife clean between each cut. Serve with optional whipped cream and/or chopped nuts.