Beat peanut butter and brown sugar until smooth. Add egg, vanilla, baking soda, and salt. Mix for about a minute. Shape into balls, and if desired roll in sugar. Flatten with a criss cross pattern with a fork, or simply flatten with the bottom of a glass. If you'd like to add Oatmeal Chocolate Chip PB Cookies, add chocolate chips and oats. Bake for 8-9 minutes, don't over-bake, and let them sit on the baking sheet for a few minutes before transferring to a cooling rack. Makes 18-20 cookies.