Over medium heat, bring milk to boil. Add sugar and cornstarch, stiffing constantly until thick. Remove from heat and stir in butter and vanilla. Cool. Refrigerate at least 2 hours or overnight. Before serving, stir in heavy cream and Kahlua. Ladle on unmolded Flan.
Recipe of La Mansion del Rio, from Arlene Lightsey's column, Chefs' Secrets, S.A. Express-News.