How to cook very large Brussels sprouts?
Steaming is my favorite way to cook them, keeps the flavor in. I'd halve the really big ones and leave it at that, there's no need to get over-complicated with it. Some will be a bit more done but that's ok. 

If you really want to jazz them up do a quick fry with them with a bit of butter, oil and slivered almonds and pine nuts. Yummy!