4. Mushrooms
Shrooms on burgers have customarily been of the cooked variety. While that remains constant, the type of mushrooms offered has changed. Before, if you ordered mushrooms, you got the basic garden variety cooked in butter or oil. Now, you may discover treasure in the form of a delicious (albeit pricey) truffle on your burger; and, like the neighboring onion, whatever type of shroom you order may be cooked in any number of ways, and bathed in a popular libation.