Combine the icing sugar, peanut butter, margarine and coconut with a fork and roll into balls a bit smaller than a ping pong ball. Chill 'til hard. In the mean time, melt chocolate squares in a double boiler.
Dip cold peanut butter balls in melted chocolate and transfer to a waxed paper lined cookie sheet. I sometimes use a combination of a teaspoon and a wooden skewer to roll the balls around in the melted chocolate. If you have any bare spots on the bonbons once you're done you can just paint them with any extra melted chocolate from the pan.
Return chocolate covered bonbons to the freezer so the chocolate can set. If you can resist eating them straight away, they do keep nicely in the freezer. Store in little gift boxes. I prefer to serve mine straight from the freezer.