Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat.

In a medium-sized mixing bowl, combine the peanut butter, granulated sugar, egg, and vanilla extract (if using). Mix until the ingredients are fully incorporated and form a smooth dough.

Scoop approximately 1 tablespoon of dough and roll it into a ball. Place the dough balls on the prepared baking sheet, about 2 inches apart.

Using the back of a fork, gently press down on each dough ball to create a crisscross pattern.

Bake in the preheated oven for 10-12 minutes, or until the cookies are lightly golden around the edges.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.