Not complicated, but a lot of work - brisket. I do several briskets a year, and in prior years it has always involved a mostly sleepless night tending the fire. This year we got a pellet grill with a hopper that will hold about 28 hours worth of fuel, and I've got all sorts of sensors to alert me when temps reach certain stages - all remotely relayed to my living room. Next weekend it gets tested.

I do several things that involve a lot of work -

About twice a year I make a 9 x 14 pan of sour cream chicken enchiladas - lots of prep work here.

I make a carrot cake that takes half a day and seems to involve every bowl and measuring cup I own.

I make a spaghetti salad that is often requested by friends to bring to gatherings - it's made in stages over two days.