Heat peanut butter and butter in saucepan until it bubbles. Turn off heat.
Add confectioner's sweetener a little at a time. Taste for desired sweetness. You may decide to use less or add more.
Stir until mixed well.
Temper White Chocolate
Use a bain marie (double boiler) to melt chocolate. Use 2 inches water in saucepan and make sure heat-proof bowl does not touch water. Use simmering water and melt ony 3/4 of the chocolate.
Once it's melted at about 110 degrees F. take off heat and add remaining white chocolate. Continue to stir.
Peanut Butter Cups
Fill silicone molds with melted chocolate, making sure to come up the sides.
Put in freezer for ten minutes.
Fill with peanut butter filling. Use a small offset spatula or butter knife to smooth the top. Freeze for ten minutes.
Top with remaining melted chocolate, which you may need to heat again.
Refrigerate for 15 minutes, before enjoying. You can keep in refrigerator for 3 weeks or freezer for up to 3 months.
Notes
To make peanut butter eggs, I suggest doubling recipe for the filling but not for the chocolate.