Using a stand mixer fitted with the whisk attachment, or a hand mixer in a medium bowl, whisk together the confectioner's sugar and heavy cream until stiff peaks form, about 5 minutes.
Add the Irish cream 1 ounce at a time and slowly mix. Taste between each addition.
Store covered in the fridge for up to 1 day.
Notes
Feel free to substitute other liqueurs, like hazelnut liqueur, coffee liqueur or almond liqueur.