These brownies get a double dose of Irish cream in both the batter and the whipped ganache topping. Slideshow: More Brownie Recipes
MAKE THE WHIPPED GANACHE Place the bittersweet chocolate in a medium heatproof bowl. In a small saucepan, combine 1/2 cup of the heavy cream with the Irish cream liqueur and corn syrup. Bring to a boil over moderate heat. Pour the hot cream over the chocolate and let stand for 1 minute; whisk until smooth and transfer to a blender. With the machine on, slowly drizzle in the remaining 3/4 cup of the heavy cream until smooth. Scrape the ganache into a medium bowl and refrigerate until thickened, about 1 hour.
MAKE THE BROWNIES Preheat the oven to 350°. Line a 9-inch square baking pan with foil, draping it over the edges. Lightly butter the foil.
In a medium bowl, whisk the flour with the salt and baking powder. In a medium saucepan, melt the 1 stick plus 2 tablespoons of butter over moderate heat. Remove the saucepan from the heat and whisk in the cocoa powder and sugar until incorporated. Add the eggs, one at a time, mixing well after each addition. Stir in the liqueur. Fold in the dry ingredients until no streaks of flour remain.
Spread the brownie batter in the prepared pan and smooth the top with a spatula. Bake for about 18 minutes, until the edges are set but the center is still soft and a toothpick inserted into the center comes out coated with a little of the batter. Transfer the pan to a wire rack and let the brownies cool completely, about 1 hour.
Using a rubber spatula, spread the cooled ganache over the brownies in an even layer. Refrigerate until the ganache is firm, about 2 hours.
The brownies can be covered and refrigerated for up to 4 days.