Preheat the oven to 350 degrees F. Grease a 2 quart glass rectangular pan with 1 tablespoon of the butter. Heat a large saute pan over medium-high heat. Add the foie gras and saute quickly for 1 minute. Remove and drain on paper towels. Set aside. Add the onions. Season with salt, cayenne and black pepper. Cook, stirring, until the onions are soft, about 4 minutes. Add the pumpkin and garlic and saute for 2 minutes. Remove from the heat and cool. In a large mixing bowl, whisk the eggs until smooth. Add the cream. Season with salt, cayenne, pepper, hot pepper sauce, and Worcestershire sauce. Whisk the mixture until blender. Add the pumpkin mixture, reserved foie gras and bread crumbs and mix well. Pour the mixture into the prepared pan. Sprinkle the top with the cheese. Bake until the pudding is golden brown and bubble, about 55 minutes. Remove from the oven and allow to cool for 5 minutes before serving. To serve, spoon the pudding in the center of each serving plate. Arrange a few slices of the venison around the pudding. Spoon the Berry Reduction around the pudding. Garnish with the sweet potato nests and parsley.