Set up an ice bath by placing a 2 quart (2 liter) bowl in a larger bowl partially filled with ice and water, and place a strainer on top.
Heat the milk, sugar, and egg yolks in a saucepan. Cook over low heat, stirring constantly and scraping the bottom, until the custard thickens enough to coat your spatula (160-170F).
Add Baileys and stir.
Churn ice cream! We love and recommend our Cuisinart churner!