The thing about proper cooking that might make him seem different is his emphasis on technique and ingredient. Most kids see the lunch lady cooking meat. He has suggestions on how to sautee properly. And frilly? Dump the frilly apron. Give him a chef's coat (and when he learns to take pride in it despite being different), a hat. In fact, that'd be what the kids understood least. "Aww, cooking with an apron." In fact, if he's dressed like my pro chef friends, he looks very professional.
The concept doesn't have to be "Boy does something frilly, gets bullied." I have good friends who are chefs, and because it has a language and art all its own, it would separate him naturally. Then again, if you've watched a full scale kitchen in flight, with the head chef and all his sous chefs at work, you know it's a machine oiled with sweat and seared in heat.
Love the idea. Lots of things for a young boy to be insecure about. Lots of things for the bullies to not understand.