Feel free to add a teaspoon of vanilla, an additional egg (for a gooier cookie – see note in recipe), a pinch of sea salt or a handful of chocolate chips, the cookies are delicious as written or with the extra ingredients. I do not recommend using a natural peanut butter for this recipe. I’ve found that a commercial peanut butter, i.e. Jiff or Skippy will work best for these cookies.
I like to remove about 2 tablespoons of peanut butter from the "cup" listed in this recipe. This results in a slightly less dense cookie that everyone loves even more than the original.
Alternatively, some readers have mentioned that they like to add an extra egg to this recipe. If you choose to add an extra egg, simply scoop the finished cookie dough onto the baking tray. It will not be firm enough to roll into balls or press with a criss-cross pattern. The cookies will be puffier straight out of the oven and then will settle a bit as they cool.