Preheat the oven to 180°C.
In a bowl, mix together peanut butter, egg, and erythritol until well combined.
Shape the dough into round balls and place them on a baking tray.
Press the tops of the cookies with a fork to create a pattern.
Bake in the preheated oven at 180°C for 10-12 minutes.
Let them cool before serving.