Is there a synonym for "top-class" you can use for chefs? I thought about "Michelin-starred", but that's too specific and not every "top-class" chef is "Michelin-starred" and "top-class" is too generic and can be used for other things than chefs. I am looking for an adjective, but maybe a noun that means "top-class chef" would do the job too.
There is very little wrong with the generic "top class"
You will be served a meal prepared by a top class chef ...
There is an expression "cordon bleu" meaning an excellent chef. There are a few problems with its use: It is a cliché, and over-use has tended to weaken its meaning. It tends to suggest chef who is skilled at classical French cooking, and it is now more usually used for a chef who trained at one of the various schools called "Le Cordon Bleu".
Given these problems, I'd not use "cordon bleu", and stick to the generic.