This is such a basic recipe, I always have the ingredients on hand.
6 T extremely soft butter
1 t vanilla
2 eggs
1 C sugar
6 T cocoa
1/2 C flour
1/2 C chopped walnuts
Preheat oven to 325 F. Combine the butter, vanilla, and eggs in a large bowl. In another bowl, combine the sugar, cocoa, flour, and nuts. Stir the dry ingredients into the butter mixture and blend well. Bake in greased 8x8x2 pan for 30 to 35 minutes. Cool and cut in squares.