Preheat the oven to 350℉. Line a baking sheet with parchment paper.
In a medium bowl, use an electric mixer to combine the peanut butter, sugar and egg.
Roll the dough into 1-inch balls and place on the baking sheet about 2-inches apart. Flatten each ball of dough with a fork in a criss-cross pattern.
Bake for 8 to 10 minutes, until the edges are firm and golden brown. Remove the baking sheet from the oven. Let the cookies cool on the baking sheet for at least 5 minutes before transferring the cookies to a cooling rack to cool completely.