Preheat oven to 375 degrees. Melt chocolate. Cool.
Sift flour, baking soda, and salt. Beat butter until soft.
Add brown sugar and eggs and beat until fluffy. Beat in vanilla and add cooled chocolate.
Stir in dry ingredients (I now use unbleached flour) alternately with sour cream, beating well. Stir in boiling water.
Pour into greased and floured 9×13 cake pan or two 9 in. layer pans. Bake for approximately 35 min. (9×13) or 25 min. (9 in. pans) or until it tests done.
Cool in pans on wire rack 10 min.
In a small bowl, whip the cream. Add the cocoa, powdered sugar, and vanilla. Lightly mix; serve on top of the “cooled” chocolate cake.