Much respect 
(that emoji is supposed to be ‘man bowing’, though I do not see it)
Not a big sweet tooth guy, but that cake does look hella delicious.
The cool thing about that cake is that the ingredients perform a little magic trick during baking and invert themselves. You fill the bundt pan with the cake ingredients first and then the flan ingredients. When it bakes, the flan goes to the bottom and the cake goes to the top (Behold the power of gravity!).
Thanksgiving’s been mentioned a few times in this thread. The thing is, I can’t think of any one particular dish on the typical American thanksgiving table that is all that complicated in and of itself. The only complexity really arises from the expectation of serving so many different dishes all on the same day.
Hence my comment about prep and timing.
A double stuffed 24 lb. turkey. Stuffing under the skin with a hand-made 3 meat sausage steeped in cream, another corn bread, chestnut, and oyster stuffing in the body. The turkey has to be brined initially, then after stuffing rotated in the oven to get it evenly browned without cooking forever. Still needed 7 hours total cooking time. Pretty complicated dish. Stuffing under the skin is a skill in itself. Lots of prep time just to make the two different dressings, plus brining the bird and making gravy. So yes, the volume of sides is part of it, but a really good bird requires some significant effort also.
Swedish bean balls, a vegetarian substitute. The gravy (sauce?) was the same but the beans had to be processed to get a meat-like texture. I forget the exact steps but it took hours and left way too many pans behind for something that was merely… adequate.
The dumb part was it was self-imposed, made out of curiosity.
I’m a big fan of prepared foods or meals that have major components of prepared foods, so I don’t have really spectacular examples of complicated meals. But one in recent memory that had me buzzing around the kitchen and demanding that everyone stay out of my way involved a beautifully marinated beef tenderloin roast that absolutely had to be done medium-rare and no more, Yorkshire pudding, garlic mashed potatoes, roast mushrooms marinated in balsamic vinegar and spices, some fancy vegetable side that I cannot remember, and of course gravy. As with a lot of cooking, the challenge was not that any one thing was all that complicated, it was the combination of it all and the problem of getting everything ready at the same time.
The dinner was a success, but I hit the wine pretty hard after everyone was served. If I had to be a chef for a living I’d probably go insane. No wonder chefs are so temperamental!
Early in our relationship, my gf suggested having my family over for xmas eve dinner. She thought of the idea of a soup fest; we’d have four or five different soups, along with some simple appetizers and breads. We’d have a soup mug for every attendee, theirs to keep at the end of the night.
The idea was to do this as a one-off, but my family enjoyed it so much that they “demanded” a repeat, and so we’ve done this each year other than one COVID19 skip.
It’s a ton of work, taking a solid week of preparations. It also forces us to decorate the house for xmas, something we wouldn’t otherwise bother with.
Absolutely nothing dumb about that. I have made many many recipes solely for curiosity of a process and to learn how things work. I’ve briefly dipped my toe into stuff like cheese making, sausage making, curing my own guanciale, lomo and bacon, lacto-fermentation, brewing and cider-making from fresh apples, cultured butter, and hosts of other things I can’t remember. Sometimes the results were great; sometimes merely so-so, but the journey is the destination, as they say.
I briefly tried my hand at home brewing. The results were ok on my second attempt, but I decided that it’s more trouble than it’s worth and went back to just buying beer at the store.
NOTE to self: if invited, RSVP for this immediately
The complex single dish I make is bastillah (spelled many ways), Moroccan pigeon pie that I’ve only ever made with chicken. It takes about half a day even if you’ve made it a number of times like I have. Eventually you end up with layers of chicken meat, a mix of blanched almonds ground with sugar and cinnamon, and a dozen eggs scrambled in the reduced spices and onions the chicken was boiled in, encased in phyllo dough. It’s a show stopper. You eat it with your fingers, hot out of the oven.
Ah, the dish mentioned in Bohemian Rhapsody…
Let him go!
Bastillah - we will not let you go!
Oh God, do I remember the most complicated meal I made. 
Inspired by watching far too much of Tony Bourdain’s No Reservations, I and my wife decided to make a selection of various Chinese/Japanese Dim Sum to sample over a couple of days (this was before my wife realized she just didn’t like meat much).
So we ended up planning and making 4 types from scratch, Char Siu filled steamed buns, ground pork/leek fried wontons, steamed shrimp/scallion/sesame gyoza, and soup dumplings. The last was the worst.
So I made the Char Siu, which involved 24 hours of marinating (no biggie, just planning) and then a few hours of prep, baking, basting and delicious smells. I made plenty, because I always freeze some to add, thinly sliced to ramen, or dice for fried rice. Lots of prep and planning, but not super complicated.
Second was the broth for the soup dumplings. Oh my god. Lots of slow, very careful simmering of the meaty pork bones to carefully extract the maximum flavor and collagen without overcooking. My older stove isn’t perfect, and my current one has similar issues with cycling from higher to lower heat which can make this crazy. There are other options, but watching was really the best bet. Also very, very careful straining to keep the stock as clear as possible. Figure 2-3 hours of careful simmering and straining, plus an overnight chill to become gelatinous.
Then the next day, it was cook everything. A couple of hours of mixing the various doughs and resting, then verrrrrry carefully chopping up the soup gel and folding in some of the matchstick char sui plus other ingredients for the soup dumplings while leaving it all scrupulously cold, then folding and pinching and setting aside to stay cool, then filling the char sui non-soup dumplings, followed by more folding and pinching.
And then the fillings for the wontons and gyoza, rolling, cutting, filling with the mix I made while watching the soup simmer. Easier, but still lots of things to put together, season and prep. Then the oil for frying, and frying the pork wontons on one burner while chain steaming things on the other.
Overall we probably spent large chunks of time over 3 days in total prep, for a (delicious mind you) feast that lasted less than an hour, plus leftovers for meals for another 2 days. But the soup dumplings while wonderful, had about an 60% failure rate (ie they’d split or leak and you’d lose most of the inner soup) and even the leftovers did not normally survive reheating). Everything else was fine, but for the work involved it’s far easier to go to a store to have someone who’s probably been making them since they were a toddler at grandmother’s knee do it.
Sausage, baked beans and jacket potato. (I’m not a cook! 
)
My local Indian does a wedding feast dish where the meat is marinated for 24 hours (and it is delicious!)
Made a lasagna for a cooking contest at a culinary school. Out of the 12, I was the only person that did not work in the restaurant industry. I made my 12 cheese lasagna. Everything except the cheese had to be made from scratch. I brought my jarred home made sauce, it was not allowed. I ground my own meat, made the sauce and pasta (3 types, regular, beet and spinach). The only thing I really wasn’t prepared for was being scored on the plating. I easily won the taste but finished 11th on the presentation. Ended up third overall. Got 3 offers of employment too. Haven’t made it in years, I can’t eat it anymore due to dietary restrictions. I posted the recipe back in 2004, it can be found by searching the site.
I did the work to save y’all 30 seconds of searching….
May I present racer72’s award-winning 12 cheese lasagna recipe (this is actually from 2002; let us know if there’s a newer improved 2004 version):
I made a large batch of Chile Rellenos, turned out very good, made enough to gorge after completion and to bring to work for the week for lunch but lots of tedious steps. I have not made them since.
Apart from regular Christmas Turkey or Lamb roasts for family plus gatherings, probably the worst was a Mezze Platter meal, after watching Yotam Ottolenghi on some version of Masterchef.
Just lots of fiddly dishes to get prepared and ready. It was nice, though, and we still use some of his ideas for light summer meals.
It’s been a while, but if I recall that’s pretty much what I did, using the small cutter on the pasta maker and then soaking them. There’s some part of me remembering mixing baking soda into the dough…but I’m not actually sure. All I know is that I was craving ramen, and the shop I had bought fresh noodles at had stopped carrying them, and I couldn’t find them anywhere, and there certainly aren’t any ramen shops around here, so I decided to just make them. And it took so much vastly longer than I anticipated.
They were good, but not necessarily better than the ones I had been buying.
I have several “for ramen” ingredients in my freezer that have just sat there for a very long time because I haven’t had the courage to duplicate the process and still can’t find good noodles.