You can't really get a "buttery" Chardonnay out of a kit unless you try and do a "battonage process"on it and that really only adds increased mouthfeel not so much butter. I would go for an Aussie styled kit as they will include oak which will help add some depth and complexity but again not really butter. Butter in a Chard comes from malolactic fermentation which is not done on kits, only fresh grape products. I would go as mentioned above the RJS EP Aussie Chard (comes with an oak teabag) . The Eclipse Chard should be great (18L kit) but it has no oak supplied you would have to add your own.