Melt chocolate and marshmallows over hot water, add the 1/2 cup hot water, beating to smooth paste. Cool. Sift together flour, salt, and soda. Beat eggs, add sugar, whip until creamy. Add sour cream and stir until smooth. Fold flour gradually into egg mixture. Carefully fold in chocolate paste and vanilla. Turn batter into well greased and floured 8" round cake pans. and bake 30-35 minutes at 350 degrees.
Creamy Chocolate Frosting: 1/4 cup butter or margarine softened. 2 3/4 cups powdered sugar, 1/2 cup cocoa, 1/3 cup milk and 1/2 teaspoon vanilla.
Add all ingredients together and mix till smooth. Frost cake after it cools.