Spag Bol sauce.
lasagna
cottage or shepherd’s pie (beef or lamb mine)
smoked fish and brocolli pie (covered in mashed potatoes, use milk from poaching fish to make white sauce)
chicken and mushrooms in creamy (white wine) sauce (good with rice/pasta/potato
curries - lamb rogan Josh, lamb bhuna, chicken vadagam, chicken tikka masala, chicken korma, chicken jalfrezi etc)
chilli - beef or vegetarian
stews and casseroles - beef bourginone (sp?), coq au vin, beef and Guinness stew, country stew with lamb, pork knuckles slow cooked with cannellini beans and apple juice (take meat off bones to freeze).
also veggies already diced up and ready to be roasted (I like Mediterranean veg - whatever you have and like of onion, garlic, peppers, courgettes, mushrooms, tomatoes, mange tout/sugar snaps, french beans etc) - freeze raw or cooked leftovers - use as side dish, base to cook roast chicken joints on, or to add leftovers to plain pasta sauce (with leftover roast chicken, or cooked bacon lardons, or cooked meatballs of sausage meat) to have easy pasta meal.
I also put chicken joints already marinated in lemon, garlic and rosemary in for an easy Greek Lemon chicken night - dump into cooking tray and roast.
Leftover mac’n’cheese (mine has bacon, mushrooms and often loads of other veg) is a great pasta bake.
When I make cauliflower cheese, I often do a second one to freeze.
And if I do a big roast, I will often freeze slices of leftover meat with leftover gravy. Reheats very well in a pot or in the oven (depending if you are doing mash or roasties for potato).