Mix the brownies according to package directions.
Add one tsp of espresso powder and mix well.
Grease an 8x8 glass baking dish
Pour half the batter in the baking dish and evenly spread along the bottom.
Break pieces of the chocolate bar - probably 3/4 of the bar and set it on top of the first layer of batter.
Add the remaining batter on the top and spread to cover the chocolate bars.
Bake according to package directions. About 43 minutes.
Let the brownies cool completely before cutting.
Dust with powdered sugar.