Preheat oven to 350°F and line two baking sheets with parchment paper.

In a medium bowl, mix together peanut butter, sugar, egg, vanilla extract, and baking soda until well combined.

Roll dough into 1-inch balls and place on prepared baking sheets about 2 inches apart.

Use a fork to press a criss-cross pattern into each cookie, flattening them slightly.

Bake for 10-12 minutes until edges are lightly golden, then cool on the baking sheet for 5 minutes before transferring to a wire rack.