Preheat the oven to 350°F (177°C) and line a baking sheet with parchment paper.
Add the peanut butter, sugar, and egg to a large bowl.
Mix until evenly combined and a thick dough forms.
Scoop the dough into approximately 12 equal portions and roll into balls.
Arrange on the prepared baking sheet.
Press each ball gently with a fork in two directions to create a crisscross pattern.
Bake for 10–12 minutes, until the edges are lightly golden and the cookies look set.
Let the cookies cool on the baking sheet for several minutes before transferring to a rack.