Bring mixture to a simmer over medium-high heat, whisking gently but constantly and scraping bottom and sides of pot. Reduce heat to medium and cook, stirring constantly, until pudding is thick and coats back of a spoon, 1 to 2 minutes.
Strain pudding through fine-mesh strainer into bowl, scraping inside of strainer with rubber spatula to pass pudding through. Stir butter, vanilla, and butterscotch or caramel sauce into pudding until butter is melted. Press plastic wrap directly on surface to prevent skin from forming and refrigerate until set, about 3 hours.
Time to Prepare: 20 minutes plus cooling time
Submitted By: Betsy
Original Source: Cook's Illustrated