Preheat oven to 350 degrees. In a medium mixing bowl, add the eggs and whisk until well blended. Add the water, oil, and Baileys, whisking until fully combined.
Slowly add in the brownie mix a little at a time and whisk until batter is smooth. Pour into a lightly greased 9x13-inch baking dish. A bigger baking dish will yield thinner brownies. A smaller baking dish will yield thicker brownies.
Bake brownies for 25 to 35 minutes, or until an inserted toothpick comes out clean. Remember that a different sized dish will affect baking times. I used a 9x13-inch ceramic baking dish and my brownies were ready at 35 minutes. Non-stick baking pans will shorten the baking time by about 5 minutes.
Allow the brownies to cool completely.
Baileys Buttercream Frosting
In a large mixing bowl, add the softened butter and Baileys. Using an electric mixer, beat until well blended. A little at a time, add in the powdered sugar and beat on low until frosting is smooth and fluffy. If the frosting is too thin, add more powdered sugar. If it's too thick, add more Baileys.
Using a silicone spatula, smooth on the Baileys Buttercream Frosting over the cooled baked brownie. Place frosted brownie in the refrigerator to cool until the next step.
Baileys Chocolate Ganache
Pour chocolate chips into a small bowl and set aside. In a small saucepan, add the heavy cream and Baileys over medium/high heat. Heat just until boiling, stirring constantly. Remove Baileys mixture from heat and pour into the bowl of chocolate chips. Allow to sit for 5 minutes undisturbed.
Whisk chocolate chip mixture until smooth and glossy. Smooth chocolate ganache over the frosted brownie and allow it to sit out for 30 minutes until placing back in the refrigerator. Refrigerate for at least an hour before cutting into squares.
Notes
Notes on Alcohol Content: Each layer of this luscious brownie dessert is splashed with silky Irish cream, making this a tipsy adult treat. If you would like to make them safe for children, simply leave the Baileys IrishCream out of the buttercream frosting and chocolate ganache. The Baileys in the brownie mix will cook off its alcohol content, leaving you with only the flavor.