The first thing that comes to mind is pre beam Old Taylor, which is hard to come by. Buttersctoch all the way. Not one bourbon on the market now has that much in it. Lots of bourbon used to have this, somebody already mentioned Old Forester. Most distilleries used to ferment hotter as they had not cooling in the fermenters. It stressed the yeast, making diacetyl and there you have it. Most have coils now as they have thickened the mash up to get more whiskey out of a fermenter. Makers Mark I am told recently just did that.