Start by making the chocolate. Place a silicon mould on a flat tray - this will stop the chocolate mould from bending when you place it in the freezer. Alternatively, you can line a muffin tray with 12 patty cake papers. Set aside.
Melt the cacao butter in a microwave or double boiler at low heat. If using a microwave, melt at 30 second intervals until the cacao butter is clear. Stir well.
Remove from heat and add the powdered monk fruit sweetener. Stir well.
Add the cocoa powder and mix well.
Divide the chocolate mixture into two and set the other half to the side (this will be for the top layer of the peanut butter cups).
Pour half of the liquid chocolate mixture into the moulds/lined tray and freeze for 20 minutes.
Remove from the freezer and then spoon a little peanut butter onto the centre of each bit of chocolate. Try to leave an edge of about 2mm.
Place the moulds back in the freezer for 15 minutes to set.
Remove from the freezer and distribute the second half of the chocolate onto the peanut butter. Then place back into the freezer to set again for 20 minutes.
Once set, remove from the moulds and serve cold.