Removing Butter Stain on Ugg Boots?

I dropped a buttery potato on my chestnut Ugg boots. In my panic, I cleaned them using the proper Ugg cleaner (which I once used successfully to get a chocolate stain out) and it hasn't budged. I did it again, and it still looks no different although it is still wet. Since I've googled it, I see I probably should have used cornstarch or baby talc instead. Is it too late for this? Is the stain unfixable now?

By Rachel