Melt the butter and chocolate in a saucepan over low heat or in the microwave (in 30 second bursts).
Remove from the stove / microwave. Stir in the peanut butter and add the sweetener to taste.
Pour into a small container lined with parchment paper.
Place in the freezer for ca 30 minutes until set.
Cut into 30 squares.
You should choose chocolate with at least 85% cocoa solids to minimise the sugar content. I like 90% chocolate.Store in either fridge or freezer and be perfectly prepared for the next time you need a treat!