Line a baking tray with baking paper and set it aside. Roughly cut the butter into cubes. Place the butter in a large microwave-safe bowl and melt on high for 40 seconds. If the butter still has solid lumps, return to the microwave for a further 20-30 seconds. Remove from the microwave. Add the powdered erythritol to the butter. Use a whisk to combine to a smooth paste.
Step 2
Microwave the butter and sweetener for 2 minutes on high. It will be runny and very hot. Remove from the microwave and take care when handling the bowl. Add 3 tablespoons of peanut butter. Whisk to combine. Microwave again for 2 more minutes.
Step 3
Add 1 teaspoon of vanilla extract and 1 cup of peanuts. If you have whole peanuts, it is recommended to roughly chop the peanuts into smaller pieces. Stir to coat all the peanuts in the mixture.
Step 4
Pour the peanut mixture into the prepared baking tray. Use a spatula or the back of a spoon to level out the mixture. Be sure to work quickly here as the erythritol will begin to harden.
Step 5
Either leave the tray at room temperature or place it in the fridge to harden faster. Break the brittle into equal-sized chunks and enjoy! 1 serving is 1oz/ 30g.