In a medium saucepan, combine butter, half and half, granulated sugar and brown sugar. Cook, stirring constantly, over medium heat for 5 to 8 minutes, or until the mixture is slightly thickened and just comes to a full boil. Remove from the heat and stir in vanilla. Serve warm.
Recipe courtesy of chef and culinary instructor Amy Tyrell of Morsels As You Wish, a Ventura-based catering company.