Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium mixing bowl, combine the peanut butter, sugar, and egg.
Stir the mixture until the ingredients are fully incorporated and the dough is smooth.
Roll the dough into 1-inch balls (approximately 1 tablespoon each) and place them 2 inches apart on the prepared baking sheet.
Using the tines of a fork, press a criss-cross pattern into the top of each dough ball to flatten slightly.
Bake for 8 to 10 minutes until the edges are just set and the bottoms are slightly golden.
Allow cookies to cool on the baking sheet for at least 5 minutes to firm up before transferring to a wire rack.