Preheat oven to 175°C. Lightly butter an 8-inch square baking pan. Line a baking sheet in the baking pan, extending the sides for easy lifting.
Using an electric mixer, beat cream cheese and butter in medium bowl until light and fluffy. Gradually add in the sugar and beat until well blended. Beat in the egg and vanilla. Fold in flour, Baileys®, and vanilla. Set mixture aside.
Lightly toast the pecans for 10 minutes. Let cool and chop them into bite-size pieces. Set aside.
Combine the baking chocolate and butter in a heat-proof bowl. Set over a pan of simmering hot water (double boiler) and melt the chocolate and butter until the mixture is smooth and free of lumps. Cool slightly.
Using an electric mixer, beat sugar and eggs in a large bowl until slightly thickened, about 2 minutes. Beat in the chocolate mixture, vanilla and 1 tablespoon of Baileys®. Fold in the flour, baking powder and salt.
Spread half of chocolate batter in the prepared pan. Using a rubber spatula, spread cream cheese mixture over chocolate batter. Spoon remaining chocolate batter over top of cream cheese mixture. Using the tip of a knife, gently swirl through batter, forming a marble design. Bake until tester inserted into center comes out with a few moist crumbs attached, about 30 minutes.
Using a skewer, randomly poke holes in the brownies and drizzle the remaining 2 to 3 tablespoons of Baileys® into the brownies, depending on how strong you want the Baileys® taste to be. Let the brownies cool in tin before lifting it out. Cut into squares and serve with whipped cream or a scoop of vanilla/Baileys® ice cream. Or even better - serve with a small slurp of Baileys®!