Cream butter and sugar. Add eggs that have been beaten well and vanilla. Add melted chocolate. Sift flour and baking powder together. Mix well and add to chocolate mixture. Add nuts. Pour into a greased 8-by-8-inch pan and bake at 350 degrees for 30 minutes.

When done, place marshmallows over top and return to over until marshmallows are melted. Remove from oven and spread marshmallows. Cool. When cool, ice with your favorite chocolate frosting.