well, if you wanna do what i'm doing... just roast a bunch of sweet potatoes and throw in a bit of roasted garlic, a dash of honey, a bit of cream, some sea salt (i'm arbitrarily using sel gris), a shitload of real butter, and either some krunchy uncured bacon or
kurobuta ham. not exactly 'casserole' but potatoes don't need to get very complicated.
also making macaroni and cheese. parmigiano reggiano, cave-aged gruyere, aged white cheddar, a bit of colston-bassett stilton (a mild blue cheese), with a dash of chipotle for smoky goodness, probably some rendered pork fat, some other piggy product, butter, sea salt, fresh ground black pepper, panko crust on top...