Melt the 1/2 cup butter and unsweetened chocolate in a medium saucepan over low heat, stirring constanly. Remove from heat, cool slightly, stir in sugar.
add eggs,one at a time. beating with a wooden spoon just until combined. Stir in vanilla.
Stir together flour and baking soda in a small bowl. Add flour mixture to chocolate mixtureand stir just until combined. Spread batter in a greased 8x8x2 inch baking pan. Bake in a 350 degree oven for 30 minutes.
Meanwhile, for topping, dissolve coffee crystals in whipping cream. Beat together powdered sugar and the 2 tablespoons butter in a small mixing bowl with an electric mixer on medium speed.
Add whipping cream mixture and beat until creaming. If necccesary, add a little additional whipping cream until mixture if of spreading consistency.
Spread over the warm brownies. Chill about an hour or until topping is set. Carefully spread chocolate frosting over brownies. Chill until frosting is set and cut into bars.
FOR THE CHOCOLATE FROSTING: Combine 1cup semisweet chocolate pieces and 1/3 cup whipping cream in small pan. Stir over low heat until chocolate is melted and mixture begins to thicken.