Preheat oven to 350°F. Line an 8×8-inch pan with parchment paper.
Place the chocolate and butter in a microwave-safe bowl and melt in 30 second intervals, stirring each time, until melted. It should only take 2-3 intervals. Set aside.
In a large bowl, whisk together the flour, cocoa powder, and salt until combined.
In a separate bowl, whip together the eggs and sugar until pale yellow and frothy, about 2 minutes.
Add the chocolate butter mixture to the whipped eggs, then add the Irish Cream. Whisk until combined. Then stir in the dry ingredients until no flour streaks remain.
Pour the batter into the square pan, and bake for about 17 minutes. The top should be shiny and set, but slightly squishy to the touch, to indicate that it’s not overbaked. Let cool completely.
To make the White Chocolate Buttercream:
Whip the butter in a bowl for 30 seconds, then whip in the caramelized white chocolate. Add the confectioner’s sugar and whip until smooth. Spread the frosting all over the cooled brownie square.
Refrigerate the brownies for about 1 hour to allow the buttercream to firm up. Then cut into squares and enjoy!
*To caramelize white chocolate, set the oven to 250F. Cut the white chocolate into chunks with a knife and spread on a baking sheet. Cook for a total of 45 minutes, stirring every 7-8 minutes. The white chocolate will get smoother and smoother, and darker and darker, each time. By the end of the cooking time it should be the color of butterscotch and completely smooth. NOTE it is very important to use a real white chocolate that’s high-quality and high in cocoa butter. Buy brands such as Valrhona, Scharffenberger, or Callebaut. A full post on it is here.