Sift the flour, baking soda and salt together in a medium-size bowl and set asi de. Place the brown sugar in a large bowl of an electric mixer; beat on high s peed about 10 seconds to break up sugar. Add the butter and beat until the mix ture is the consistency of wet sand, about 1 minute. Beat in the eggs one at a time until well blended, about 10 seconds each time. Add the corn syrup and v anilla and beat until smooth, about 5 seconds. Beat in the cooled chocolate un til well blended and smooth, about 3-5 minutes, scraping bowl sides well. Add flour mixture and buttermilk alternately to chocolate mixture, beginning and en ding with flour and beating after each addition just until smooth. Pour equal amounts of the batter into three 8-inch round greased and lightly floured cake pans (1 1/2 inches deep). Bake at 350 degrees until centers spring back when l ightly pressed, about 35 40 minutes. Remove cake layers from pans to a wire rack and glaze while still hot. Cool thoro! ! ughly. spread generously with icing between layers and on top and sides.
GLAZE: In a small saucepan combine the water and sugar; bring to a boil. Remo ve from heat and stir in the vanilla. With a pastry brush, brush hot glaze ove r the surface and a little on the sides of each cake layer, using all the glaze . Makes about 1 cup glaze.
MOCHA ICING: Cream the butter in a large bowl of an electric mixer on high spe ed until very creamy, about 2 minutes. Gradually add the sugar and beat until smooth, about 3 minutes.
In a separate bowl, combine 1/3 cup of the cream and the remaining ingredients, stirring until thoroughly dissolved. Add cream mixture to the butter mixture . Beat until well blended and sugar is completley dissolved, about 5 minutes, scraping bowl well. Thin with a little more cream if desired. Makes enough fr osting for one 3-layer cake.