Step 1Heat the oven to 350 degrees. In a mixing bowl, combine 4 tablespoons of the cocoa with the sugar, flour, baking powder and salt. Toss with a fork until well mixed.
Step 2Stir in the half-and-half and butter and mix well. Fold in the nuts. Spread the batter evenly into a 9-inch round or square baking dish, smoothing the top.
Step 3Combine the remaining cocoa with the brown sugar, mixing well, and distribute evenly over the top of the batter. Pour 1 3/4 cups hot water evenly over the top.
Step 4Bake 45 minutes. Remove the dish to a trivet to cool slightly and scoop the pudding onto dessert plates, with or without ice cream.