Aroma 2 is butter. The distinctive scent of butter is from the impactful aroma 'Diacetyl'. In wine, this compound gets naturally produced during a process known as 'malolactic conversion' where sharp, green-tasting malic acid is converted to softer, creamier lactic acid. The buttery aroma of Chardonnay is down to this conversion process, lending a creamer mouthfeel, and sweet smelling butterscotch notes, which has a good affinity with the spice and vanilla notes from oak ageing.  Not all white wines will undergo this conversion, preferring to retain a more linear, crisp mouthfeel and purely primary fruit flavours. However when done well, and balanced with ripe fruit flavours, this can create some of the most thrilling, luxurious wines in the world.