In a large mixing bowl, combine your peanut butter, 2/3 cup of the erythritol, baking soda and egg and mix well. Cover and refrigerate for 30 minutes.
Preheat the oven to 180C/350F. Line a large baking tray with parchment paper and set aside. In a small bowl, add your remaining 1/3 cup of sweetener with cinnamon and mix well.
Remove the cookie dough from the fridge. Using your hands, form 12 small balls of dough. Roll each ball of dough in the cinnamon/sweetener mixture until completely covered. Place the covered balls of dough on the lined tray and press each ball into a circular shape. Press down on each cookie with a fork, in a criss-cross shape.
Bake the cookies for 10-12 minutes, or until just done. Remove from the oven, sprinkle with more of the cinnamon/sugar mixture and allow to cool completely.
See the post for the vegan/eggless option. To replace the egg, substitute it for 3-4 tablespoons of ground chia seeds. Start with 3 tablespoons, then add an extra tablespoon if needed.
To store. Store snickerdoodle cookies in a sealed container at room temperature. They will keep fresh for up to 2 weeks. Alternatively, you can refrigerate them, and those will keep for up to 1 month.
To freeze. Place cookies in parchment paper and place them in a ziplock bag or shallow container. Frozen cookies will keep fresh for up to 6 months.
To thaw. Allow cookies to thaw at room temperature or in the refrigerator overnight.