Melt peanut butter. Add it to a bowl with maple syrup, 2 Tbsp. oat flour, cinnamon, and cream of tartar. Mix to combine; the mixture should come together in a ball and should be smooth. If the mixture isn’t coming together, add another Tbsp. of oat flour.
In a small bowl, combine sugar and cinnamon for the topping. Set aside.
Roll peanut butter mixture into small balls (I got 15-16 balls out of the batch). Roll each ball in the sugar/cinnamon mixture, and place on a parchment-lined plate. Place in the freezer to set for about an hour.
Meanwhile, melt your dark chocolate.
Once the buckeyes are set, remove them from the freezer and dip them in the melted chocolate with a toothpick, leaving the tops exposed (see photos). Set each buckeye back on the parchment-lined plate and set in the fridge to set. Store buckeyes in an air-tight container in the fridge.