In a large bowl, combine all the ingredients—peanut butter, sugar, and egg—and mix until the cookie dough thickens slightly.

Using a small cookie scoop, tablespoon, or spoon, form small cookie dough balls and place them on a parchment paper-lined baking sheet. Gently flatten the cookies with the back of a fork to create the classic criss-cross pattern.

Bake in a center oven rack at 350°F for 8-10 minutes or until the edges turn a golden brown.

Let the cookies cool on a wire rack for a few minutes before serving.