Butterscotch Pudding

Saw a butterscotch pudding recipe recently on David Lebovitz's blog and really wanted to try it. I've only ever made the kind that comes in a box from Jello. Making it from scratch was not overly complicated and it tasted really good. I still don't totally get where the butterscotch flavor comes from. One minute it's milk and brown sugar and eggs, the next minute it's sweet delicious butterscotchiness. Okay, there were a few other ingredients... melted butter, vanilla, salt, dark rum. I had to make a special trip for one of those little airline bottles of rum. I only needed two teaspoons for the recipe. This is an easy one to try at home that doesn't require any special equipment.