Step 1

In a small bowl, mix together brown sugar, cornstarch and salt. Add enough milk to make thick paste. In a saucepan over medium heat, bring milk to a boil. Stir in brown sugar mixture, return to a boil, and cook for 1 minute.

Step 2

Place egg yolks in small bowl. Temper the yolks by quickly stirring in about 1/4 of hot milk mixture. Pour yolk mixture back into hot milk mixture, and return to heat. Cook, stirring constantly, for 1 minute; remove from heat. Stir in butter and vanilla until butter is melted. Pour into bowls, and let cool slightly.