I made good brussels ONCE. I have the recipe and tried to do it many times, never could make them good again, always too bitter. I know it's possible but I'll wait a decade for stars to align again.
Brussel sprouts literally have become less bitter over the last few decades, but depending on where you get yours they might still be using older variants. Maybe try a different source?
I literally just clean mine, cut them in half & remove stems, toss them with olive oil & salt & pepper, then roast them cut-side down. Perfect every time.
I'm personally annoyed that I can't find the bitter ones where I am. I used to pick and east the ones my mother grew in her garden raw. All of the ones I can find now don't have the right flavour.
How much parmesan did you grate over the brussel sprouts after they came out of the oven? Whatever amount it was, you didn't do enough. Also if you forgot lemon zest, add some too.
Had both. So many people here have recommended different Brussels sprout recioes that I want comment on this. But steamed or boiled broccoli just sucks compared to seared or roasted.
Brussels sprouts, not the small bitter little bitches, but the big, fat, tiny cabbages cut in half and fried, tossed with sea salt and a sweet/sour or sweet/hot sticky sauce is so good you'll want to punch a baby in the face.
Cauliflower, pickled, tossed with cornstarch and fried, top with bbq sauce. OR toss with oil, salt, curry powder and roast will make you question your previous life and the regrets of time wasted not shoveling it into your face hole.
Source: 35+ years making food so good people would line up to smell your breath after a meal.
And my go-to is to make Carbonara, but replace the Lancaster/Guanciale with 2-3 of the outer, leathery savoy leaves cut into black width strips (vegetarian carbonara, basically).
Another option:
Green cabbage, steamed with butter melted over the top while its hot.
And cauliflower? Have you not heard the good word about cauliflower cheese bake?