In a small nonstick skillet or pan, add the butter, peanut butter and sweetener. Cook over low heat while stirring until all the ingredients have melted. Stir with a rubber spoon without letting it stick from the bottom for a few minutes until the mixture is reduced a little.
Add the whole peanut and xanthan gum, mix until fully integrated into the mixture.
Pour the mixture on a nonstick surface, it can be a tray covered with wax paper or a silicone mold that you have available.
Take the mixture to the refrigerator for about two hours until it is firm if you want your bars to be hard, place them one hour in the freezer.
Unmold the bars, cut them into 8 pieces of similar size and sprinkle with sea salt. If you wish you can sprinkle with a little keto-friendly chocolate syrup.