Not quite ready to indulge that particular sandwich, I was reminded of the Congo Bars I would make and send to him at college, decades ago. The bars are still appreciated.
Preheat oven to 350F.
2/3 cup butter, melted
2 cups dark brown sugar
2 3/4 cups flour
2 1/2 teaspoons baking powder
1/2 teaspoon salt
12 ounces semi-sweet chocolate morsels
1 cup walnuts or pecans, chopped
1 teaspoon vanilla
In a mixing bowl, combine butter and sugar.
Add eggs one at a time and beat well.
In a separate bowl blend flour, baking powder, and salt.
Add dry mixture to butter mixture.
Stir in chocolate, nuts, and vanilla.
Put into greased 9x13 inch baking pan.
Bake for 25-30 minutes, do not over bake.
Cut while warm.