What to use instead of cheese?

If you mix an egg into your white sauce first ? For the top bit I mean.

Add plenty of seasoning and mustard powder to the white sauce then top with breadcrumbs and chopped parsley.

Crushed chickpeas

I'm vegan so I use Engevita nutritional yeast instead of cheese. It looks like flakes of fish food but has a savoury, cheesy taste. It's best sprinkled on after cooking as high heat can destroy it's vitamins.

Already some good ideas. Stirring something into the white sauce is a good idea as it can lift the sauce and it doesn't have to be the same ingredient/s each time. Pesto or houmous are some of the additions I have added.

Thank you all! I'll try some of these to ring the changes. It's one of the reasons I've never eaten a take-away pizza, and Italian restaurants are an occasional treat although they are very good at leaving out cheese if requested. I dream of trying a Domino's pizza, believe it or not!!!

Mushroom sauce instead of white sauce. I make it for GS on pasta someones. It's yummy.

Onion sauce. Parsley sauce.

Herby breadcrumbs scattered over the top add a bit of extra texture. If your husband can tolerate grated parmesan cheese, then you could mix a bit of that into the breadcrumbs too.

What about using vegan cheese? Does that upset your H's stomach?

Mustard powder and Engebita yeast flakes added to white sauce has a nice "cheesy" taste

All brilliant ideas, thank you! I think I could sneak in a bit of parmesan as it's not runny and gloopy. I know, from discussing this with him numerous times, that it's the texture that is more of a problem than the actual taste. As I said before, he can eat "raw" cheese -even mature Cheddar but not blue cheese. That is a step too far! He even eats Camembert sometimes but "hot melted" cheese is a no-no! Onion sounds good, and herby breadcrums too. I will be experimenting with all of your suggestions over the coming weeks and will report back!

An egg in the white sauce and some nutmeg