1/2 cup butter
1 cup white sugar
1 teaspoon vanilla extract
1/2 cup all-purpose flour
1/3 cup unsweetened cocoa powder
1/4 teaspoon baking powder
1/4 teaspoon salt
1/2 cup chopped walnuts (optional)
Preheat oven to 350 degrees F (175 degrees C). Grease a 9 x 9 inch baking pan.
Melt butter in a small sauce pan. Add sugar and mix well and cool slightly (enough so eggs won't cook when the mixture is added to them).
In a medium bowl, beat eggs. In small bowl combine flour, cocoa, baking powder, and salt ina small bowl.
Gradually stir the butter/sugar mixture into the egg mixture. Add the vanilla. Add the flour mixture and mix until well blended, being careful not to beat the mixture.
Stir in walnuts, if desired. Spread the batter evenly into the prepared pan.