I have in my freezer some lamb neck cutlets (from half a lamb I bought from a farmer), but I am not sure how to cool them. Is slow-cooking the way to go or would they be ok just pan-fried? Or does anyone have any other suggestions?
I would definitely say slow cooker. It's a cheap cut so the slower the better.
A very standard traditional disk would be Lancashire hotpot.
There will be loads of recipes on the internet but, for example:
Brown an onion and any chopped-up vegetables you have to hand (e.g. carrots, celery, leeks - though some pedants purists say there shouldn't be carrots in a LHP). Brown the cutlets (not sure if this is really necessary. Add stock/water/red wine to cover. Bring to simmer, add seasoning, and transfer to slow cooker and cook on the low setting for 4 or more hours.
If you don't like too much fat, you could cook it the day before you need it, let the dish cool when it's done. Put it in the fridge overnight. Then the fat will solidify on top and you can easily lift it off then reheat the (relatively) fat free version.