In the Extra Trimmings level Night of the Hangry Horde just get past the initial Onion King speech. When the first stage pops up so will two Unbread, simply run over them with the van, you don't even have to wait for them to get back up.
Alternatively if you have started Overcooked! 2 there are four Unbread around the starting point, after completing the tutorial and the Onion King speech you are able to run them over.