Well, that went well - sort of.
During my cookathon I thought that I'd try Kievs.
The first batch of two was a disaster - garlic butter leaking out everywhere. However, the next two batches were fine. The trick is to seal the pocket whilst the butter is still very cold or even frozen. It's a quick flash fry thing holding the pocket opening next to the pan for 30 seconds or so. Then turn once or twice for two minutes to seal everything and make the coating stick, then bake for 20 mins or until golden brown.