In small heavy-bottomed saucepan, bring 1/2 cup of the milk to a boil. In a small bowl
, whisk remaining 1/4 cup milk, egg yolks and sugar until smooth. Whisk in flour
. Whisk a little hot milk into egg yolk mixture. Stir egg yolk mixture back into saucepan. Cook over medium heat, stirring constantly, until thick, and mixture comes just to a boil, 3 minutes. Reduce heat to medium-low; cook 2 minutes, stirring constantly. Remove from heat. Stir in vanilla. Pour into small bowl, cover surface directly with wrap; cool to room temperature. Refrigerate until cold.