There's a legend that defenders of Geneva in the Middle Ages kept out attacking hordes of Savoy troops by dumping scalding hot cabbage soup on their heads, prompting them to rename the variety "Savoy" as a taunt that would echo through eternity. That bit of history was plucked out of a half-remembered tour of Geneva, so you can trust that it's 100% accurate.
All sorts of cabbage -- which, surprise, is another brassica -- are in season during the winter, but Savoy is closer to a lettuce, texture-wise, than other varieties, making it more versatile. But do as the Genevese did, and turn it into a soup; maybe even throw it in a borscht, which is either a fancy word or Ukrainian name for "beet soup."
How's this for economy: buy one root, and it'll last you a month, depending on how often you make Bloody Marys on sad Sundays that should be spent writing your novel. Fresh horseradish is a refreshing way to add that nasally wasabi heat to, say, a quick pickle of beets and whatever other root vegetables you have on hand. Stop the presses: horseradish is ALSO A BRASSICA. There's no limit to what those things can do!