I make these ALL the time! They are SO delicious--there are hardly ever any left overs... ;)
1/2 cup flour
1/3 cup cocoa
1/4 teaspoon baking powder
1/4 teaspoon salt
1/2 cup butter
1 cup sugar
1 teaspoon vanilla
2 large eggs
1 cup walnuts, broken into pieces (optional)
Preheat oven to 350 degrees. Line a 9" square pan with foil and butter the foil. Sift together flour, cocoa, baking powder, and salt. Melt butter in a 10 - 12 cup saucepan over moderate heat. Stir in sugar and vanilla, and add eggs one at a time. Stir in dry ingredients, and stir in nuts. Spread smoothly in prepared pan. Bake 20 - 25 minutes, or until toothpick inserted in the center just barely comes out clean.
Cool in pan 15 minutes. Cover with rack and turn pan over. Remove pan and foil lining. Cover with a cutting board and turn back over again.