Grease 4-6 2-cup ramekins, or a 2 quart casserole dish. Set aside. Preheat oven to 350 degrees.
In a large mixing bowl, stir together the flour, 2/3 cup granulated sugar, 2 Tbsp. cocoa powder, baking powder, and 1/4 tsp. salt. Set aside.
In a small mixing bowl stir together the milk, nuts, melted butter, and 1 tsp. vanilla. Add to the dry ingredients and stir to combine. Pour into ramekins or casserole dish.
Bake 30 minutes. Top with vanilla ice cream and serve immediately.
In another bowl, stir together the brown sugar, 1/4 cup granulated sugar, 3 Tbsp. cocoa powder, 1 tsp. vanilla, and 1/8 tsp. salt. Sprinkle the mixture evenly over the batter. Pour the boiling water evenly over each ramekin, or casserole dish.