Preheat the oven to 180C/350F degrees.
Place the butter and erythritol (sugar substitute) in a bowl and mix together until a smooth mixture.
Add the egg, vanilla essence and peanut butter and mix until well combined and smooth.
Add the remaining ingredients and blend until combined.
Line a baking tin with parchment paper.
Place about a teaspoon of the mixture onto the parchment paper and keep about an inch apart (the cookies will spread during cooking). I cooked these in two batches on one tray.
Bake for 15-20 minutes until golden.
Remove, let cool, eat and enjoy!