Lasagna. I have an authentic family recipe, worth every minute and every calorie. But, it's a pain to make!
I don't consider stew or pot roast to take a long time, because I throw them in the crockpot after the initial prep. They cook for a long time, but the prep is fairly short. Ditto for my homemade bolognese.
Thanksgiving is a production, but I consider it a labor of love. The homemade gravy is always a killer. I do sides in the crockpot, as much as possible. Our attempt at homemade cranberry sauce last year was a bust, so I'm off the hook there.