Melt the butter and add the sugar and water.
Stir over moderate heat until dissolved, then bring to the boil. Cover with a lid, cook for about 3 minutes, or until the steam has washed the sugar crystals down from the sides of the pot.
Boil until soft ball stage has been reached (when a little syrup is dropped into iced water it forms a ball which flattens of its own accord when picked up with the fingers. About 25 - 30 minutes).
Remove from heat and pour over popcorn, stirring gently to coat completely.
When cool enough to handle, mold into balls or lollipops, and insert a small stick, if desired.