Mongolian Beef was invented in San Francisco. Most people I bet would expect a spicy hoisin sauce on a bed of crispy noodles with some kind of onions.
From Wikipedia.com
"Mongolian Beef is a dish served in Chinese-American restaurants consisting of sliced beef, typically flank steak, and stir-fried with vegetables in a sweet and savory brown sauce, usually made with hoisin sauce. The beef is most commonly paired with scallions or mixed vegetables and is often spicy. Most often, the dish is served over crispy fried cellophane noodles or steamed rice."

"The name of this dish is somewhat misleading, because neither the ingredients used (besides the meat) nor the preparation methods applied have anything in common with traditional Mongolian cuisine. The term "Mongolian" is rather meant to imply a vaguely "exotic" type of food."

I grew up on my mom's pot roast which was overbaked making it very dry and kind of crunchy on the outside which is how a like it now. That does not make it the "right" way to make it, though.