How to Make It
Preheat the oven to 350°. Lightly butter a 13-by-9-inch baking dish. In a small bowl, using an electric mixer, beat the butter with the cream cheese until smooth. Beat in the sugar, scraping the bowl occasionally. Beat in the egg, then add the pumpkin puree, vanilla, cinnamon and ginger. Stir in the flour.
Combine the semisweet chocolate and butter in a medium bowl. Set the bowl over a saucepan with 1 inch of simmering water and stir occasionally until melted. In a large bowl, combine the eggs with the sugar, vanilla and salt; set the bowl over the saucepan of simmering water and, using an electric mixer, beat at low speed until blended. Increase the speed to medium and beat until the mixture is warm to the touch. Remove from the heat and continue to beat until the mixture is think and fluffy, about 5 minutes. Using a large rubber spatula, fold in the melted chocolate. Sift the flour over the warm batter and fold it in just until combined. Fold in the walnut pieces.
Spread the chocolate batter evenly in the prepared pan. Using a tablespoon, drop dollops of the pumpkin batter all over the top. Using the back of a butter knife, swirl the pumpkin batter into the chocolate; don't overdo it or the swirl pattern will be lost. Bake for about 50 minutes, or until a skewer inserted in the center comes out clean. Let the brownies cool completely before cutting.