Cream 1/2 cup of the butter with sugar. Add eggs and beat until light. Add vanilla. Melt remaining butter with chocolate; cool, and beat into first mixture. Add flour, salt, and nuts. Mix well and pour into greased and floured pan (13 x 9 x 2 inches.) Bake in preheated moderate oven (350 degrees) for about 35 minutes. Cool in pan and cut into small squares.
NOTE: original recipe called for 3 eggs and 45 minutes of baking.