The term “buttered eggs” might bring eggs cooked with butter to mind. But in Cork, Ireland, it once meant rubbing butter on the eggshells of whole, unbroken eggs.

That might seem counterintuitive. Why waste butter on the outside of an egg? But clever Irish farmers had hit on buttering eggs as a way to preserve them during winters, when hens produce less. Taking freshly-laid, still-warm eggs, farm families rolled them in their buttery palms. The butter helped solidify the hot, brittle shells, sealing off the yolky contents from the outside air.

Buttered eggs take on a shiny gleam. And, as an added bonus, the taste of butter permeates the egg, making it even richer when cracked opened and cooked. Eggs preserved this way keep for up to six months in a cool place. It’s not surprising that buttered eggs were a Cork specialty, seeing as it’s also home to the Cork Butter Museum, a tribute to the region’s status as a butter-producing powerhouse.