At three meals a day, "five different dishes" ain't gonna cut it for more than a day and a half. Sadly below a seven day trip, let alone 20.
If you are cooking for a crew, they do not want the same food every week, so the cook needs to have a bit of depth.
I'm sorry, Mr. Demanding High Maintenance skipper, I didn't realize you require your eggs done a different way every damn morning, and a prepared lunch every day. and a new and exciting main every evening.
What is the big deal with different ways to cook eggs? Fried egg sandwiches, scrambled eggs, one-eyed eggs, poached eggs on a muffin all split up with biscuits and gravy, yogurt, fruit (while it lasts), cereal bars, crepes, pancakes, ...
Part of doing a good job as cook (I can't speak to being a chef as I by no means put myself in that category) is reuse. Another part is mixing things up. Azores to Bermuda, Norfolk to Tortola, or San Francisco to Hawaii you may have chicken a bunch of times but it can easily be different each time.
Chicken - broiled, stir-fried, marinated different ways, with pasta, with rice, with couscous, shredded in tacos - be creative.
Reuse is equally important. Roast a pork loin and vegetables. Make a lot. Leftover veg go into omelets or into scrambled eggs. Leftover pork sliced thin into sandwiches and/or mock barbeque (homemade canned sauce or something in a bottle) then shredded into tacos or burritos.
I carry an old-fashioned hand-crank meat grinder that can turn nearly any leftover protein and many starches into patties.
Be creative. Have a back-up. *grin* We all have failures.
I've sailed with people that are happy with ham & cheese sandwiches every day for lunch, and something from a can every night. Cruising doesn't have to be camping. Eat well. Enjoy.
Grilled cheese with spam, grilled cheese with ham, grilled cheese with baloni(sp?) and plain grilled cheese... I can do all of these sandwiches...And may throw in a PB & J also.
PB&J is an acceptable back-up.
Grilled cheese can be wonderful. Homemade bread, decent cheese, a slice of tomato, some ham or bacon - very nice. Good for breakfast, lunch, or midnights. It's mild, doesn't disturb fragile stomachs, is fast and easy, and most people like it.
I should note that there is definitely a place for canned goods, especially as you get further offshore. It's nice to have the flexibility and depth of choices that won't go bad. Not as good as fresh veg but a little thought will contribute to a good meal.
I think the most important element is to consider how you cook at home and not try to overhaul your approach to feeding people. A skipper I greatly respect stocks up on frozen dinners and prepared foods. He doesn't cook and won't ever be a cook. I've done side-by-side deliveries with him and fed his crew on landfall. He's a better sailor and skipper than I am. I am a better cook than he is. We can both move the boat and keep everyone happy and healthy. If you're going to try to change your style or upgrade your skills start at home.
Oh - no Spam on my boat.