Line a 13x9x2-inch baking pan with heavy foil, extending foil over edges of the pan. Butter the foil; set pan aside.
In a heavy large saucepan, heat 1 cup butter and chocolates over low heat, stirring constantly, until chocolate is melted and smooth. Set aside to cool slightly. In a medium bowl, stir together eggs, granulated sugar, brown sugar, coffee liqueur and vanilla. Stir into warm chocolate mixture; cool to room temperature.
In a small bowl, stir together flour, baking powder and salt. Fold flour mixture into chocolate mixture. Spread the batter in the prepared pan.
Bake in a 350° oven for 35 to 40 minutes or until brownies appear shiny, begin to crack on top and appear set. (Do not overbake.) Cool completely in pan on a wire rack; then cut into bars. (For cleaner cuts, you can chill brownies in pan in refrigerator for several hours. Use foil to lift chilled brownies out of pan before cutting.)
For glaze: In a small bowl, stir coffee liqueur, 1 teaspoon at a time, into 1 cup of powdered sugar, to reach drizzling consistency. Drizzle over cooled brownies. Garnish with chopped chocolate-covered espresso beans.