Preheat oven to 350° F. Line a cookie sheet with parchment paper or a silicone cookie liner. In a medium bowl, combine the sugar and egg, and mix well for 2 minutes with a hand mixer on low, or wire whisk.
Add the peanut butter to the mixture. Using a hand mixer, mix well for about 2 minutes. Make cookie dough balls. I used an ice-cream scoop to ensure equal cookie size throughout.
Place each cookie dough ball onto the cookie sheet two inches apart. Gently press the cookie with a fork vertically, then again horizontally to flatten each cookie.