I would have said the same thing but my wife and I just beat it after watching this video. No assist mode on. We thought it was going to be impossible, but this video totally saved us. We actually had 868 with a minute left the time before (which was the benchmark we were shooting for), and I panicked and didn’t get my third onion on. So we played one more time and got our 15th order at the buzzer.
We finally did it! It is possible. For the blue player make sure to prioritize queueing up at least one onion (preferably 2) and having the dish ready right when the soup is done cooking. Otherwise you're losing time.
@Ebiru2387 each ingredient once placed to cook increases the time it takes for the whole thing to finish. To counter this you place them 1 after the other as quickly as possible so that that penalty is removed from the equation. Thus allowing you to cook faster than usually possible.