Melt butter in your smallest saucepan. Remove from the heat.

Add chocolate chunks and stand for a few minutes. Meanwhile, place 12 mini-muffin papers in a tray or on a plate.

When the chocolate has melted, stir the chocolate and butter until smooth. If there are still some unmelted chunks, pop back on a low heat for a few seconds.

Place a teaspoon of melted chocolate in the base of each mini-muffin paper. Use the teaspoon to push the chocolate up the sides of the papers. Then pop in the freezer for 5 minutes to set the bases.

Combine peanut butter and icing (powdered) sugar or erythritol. Taste and add more sweetener if needed.

Divide peanut butter mixture between the mini-muffin papers. Top with remaining chocolate mixture, so no peanut butter is visible.

Refrigerate for 20 minutes or until ready to serve.