“For a restaurant the Mashgiach doesn’t have to know anything”
He has to know more than bugs and oven lighting protocols. He doesnt even need to know bugs if they demand the establishment buys pre-checked with a hechsher they like and all he must know is, how to read the name on a label. Mashgichim should be aware of what things that might be prepared look like. I will never forget the time I came into a kitchen to relieve the AM mashgiach and something was sizzling on a grill. I was told by my fellow mashgiach “they are grilling a bunch of burgers”. Because the burgers looked kid of funny I took a closer look. They were not burkers. The chef (a mechallel shabbos) was kashering livers on the broiler! To the credit of the Rav Hamachshir of the establishment, this fellow was promptly let go from his position until he was able to pass a very thorough test administered by the kashrus agency.