Preheat oven to 190°C | 375°F. Prepare two baking trays with parchment/baking paper and set aside.
Combine together peanut butter, sweetener (or sugar), egg and vanilla in a medium-sized bowl and mix well. Scoop out 1 tablespoon of cookie dough per cookie; roll into a ball and flatten with the palm of your hand (or use the end of a fork).
Bake for 10-15 minutes or until golden. Remove and allow to cool for about 10 minutes before transferring to a wire rack to cool completely.
While cookies are cooling, melt chocolate and butter (or shortening) together, mixing until smooth. Dip each cookie halfway into the melted chocolate, allowing any excess chocolate to drip back into the bowl. Place onto waxed paper; sprinkle with salt flakes and allow to set.