This recipe originally came from the 1943 edition of The Good Housekeeping Cookbook. I have used it often and it never fails to receive the thumbs up from anyone who likes brownies.
1/2 cup (100 g) unsalted butter
1 cup sugar
2 eggs, lightly beaten
60 g baking chocolate (the darker, the better), melted and lightly cooled
3/4 cup flour, sifted
1/4 tsp baking powder
1/4 tsp salt
3/4 cup chopped nuts or whole raisins (I have used both walnuts and hazelnuts with good results and I think macadamias or pecans would be good too. 50/50 nuts and white chocolate chips would be good too)
Mix together the flour, baking powder and salt.
Beat the butter until it is light and creamy. Gradually add the sugar. Add the eggs and melted chocolate and mix well. gradually add the flour mixture. Fold in the nuts/raisins. Pour batter into a small, greased oven pan and bake at 170°C for 30-35 minutes, or until the cake feels firm when the middle is pressed lightly with a finger.
Remove from the oven and immediately cut into serving-size squares.
Icing sugar may be sprinkled over the squares for an extra touch of sweetness.