How do I successfully mold butter? I have candy molds. I tried melting the butter and pouring it in, but very few of them set up. Do I have to clarify the butter first?
You're trying too hard. You can do all sorts of things with butter that is around room temperature. Between 60°F (16°C), where it becomes spreadable, and 85°F (30°C), where it begins to melt, you can mix in everything from herbs and cheese to stock and fruit puree. It is also at that point where the butter is fairly loose but definitely not melting that you can easily push it into candy molds or other forms. A small offset spatula will help you push it into the corners and smooth the top.
When you melt butter, you permanently change its structure, so that its fat, water, and milk solids become separated. For all practical purposes, you can't put that genie back into the bottle. You can indeed clarify the butter and pour that into your molds and chill, but it's really more trouble than you need to take.