1. Preheat oven to 325'F. 2. Melt chocolate on a large square of aluminum foil in a very low oven, bringing up edges of foil to prevent spillage. Cool to room temperature. 3. Grease and flour an oblong shallow baking pan, preferably glass, 12x8x2". 4. Sift flour, baking soda, and salt onto waxed paper and set aside. 5. Beat butter in a large bowl until very light and fluffy (easier with an electric mixer). Add brown sugar and beat until very fluffy and no trace of sugary "grittiness" remains. Add eggs and beat until well blended, then stir in melted chocolate and vanilla. Add flour mixture alternately with sour cream, beating after each addition with a wooden spoon. Add boiling water and stir in well. 6. At this stage the batter will be thin. Pour at once into prepared pan and bake in preheated oven for 35-40 minutes, or until cake tests done. Turn out onto cake rack and frost with Chocolate-Peanut Butter Frosting (recipe follows) or cut into squares and serve with whipped cream or vanilla ice cream

Brown sugar,firmly packed