Here is an adaptation by American Profile Magazine of the possible first brownie recipe. Fannie Farmer may have been the first to publish a brownie recipe in a cookbook.
Here’s Farmer’s original Brownie recipe from the Boston Cooking School Cook Book, 1906 edition:
1 cup sugar
1/4 cup melted butter
1 egg, unbeaten
2 squares Baker’s chocolate, melted
3/4 teaspoon vanilla
1/2 cup flour
1/2 cup walnut meats, cut in pieces
Mix ingredients in order given. Line a seven-inch square pan with paraffine paper. Spread mixture evenly in pan and bake in slow oven. As soon as taken from oven turn from pan, remove paper, and cut cake in strips, using a sharp knife. If these directions are not followed, paper will cling to cake, and it will be impossible to cut it in shapely pieces.