Preheat oven to 325

In a large mixing bowl, beat peanut butter, sugar, egg, and vanilla until well blended.

Form cookie dough into 3/4" ball and place on parchment lined baking sheet.

Flatten cookie making a criss-cross pattern with a fork.

Bake for 10-12 minutes, until lightly browned. 

Cool for 2-3 minutes on baking sheet before transferring to a wire rack to complete cooling.

Yield approx. 18 cookies.