Melt chocolate in ⅓ cup coffee over very low heat, stirring constantly. When melted, set aside to cool slightly. In a mixing bowl cream butter and brown sugar. Add eggs one at a time and beat well. Add vanilla and blend in chocolate. Beat well. Combine and fork-sift dry ingredients and add alternately with 1 cup coffee, mixing just enough to combine, by hand or on lowest mixer speed.
Pour batter into two well-buttered 9-inch cake pans lined with buttered waxed paper. Bake at 350º F for 30 minutes, or until a toothpick inserted in the center comes out clean. Do not remove cake too soon or it will fall. Cool 10 minutes in pan, then remove and coolon rack. (Layers are fragile; handle carefully.) Frost with Dark Chocolate Frosting.
Melt chocolate in a double boiler. Add butter and stir until blended. Pour into a mixing bowl. Beat in confectioners’ sugar and salt alternately with a few drops of strong coffee at a time until frosting reaches the proper consistency. Beat in vanilla.