Preheat the oven to 350 degrees.

In a medium bowl, mix together peanut butter, sugar and egg until smooth.

Fold in chocolate chips. (optional)

Roll dough into one-inch balls with your hands and place onto a Silpat or parchment-lined baking sheet. The dough will not spread, so you can make this whole batch on one sheet.

Press down with the back of a fork and then press again from the opposite direction, to form the criss-cross pattern.

Bake cookies for 12 minutes and then allow to cool on the baking sheet.

Store in an airtight container.