Black garlic started life as a white clove - how does it get black?
The slow process relies on a nonenzymatic browning reaction described in 1913 by this serious Frenchman and named for him - the Maillard reaction. Sugars and amino acids are rearranged over and over to provide colour but more importantly flavour in the black garlic. The molecules produced are specific to the food type: for black garlic more S-allylcysteine and S-allyl-mercaptocysteine and higher antioxidant levels. This is why your unbaked cake smells so-so, but your baked cake smells and looks delicious. More here - happy browning!