Selleriepüree: an earthy, velvety Swiss mash combining sweet roasted celeriac root with floury potatoes, whipped with rich alpine butter, cream, and freshly grated nutmeg.
Place the celeriac and potato cubes into a large pot of salted water. Bring to a boil and cook for 18 to 20 minutes until completely tender.
Drain thoroughly and steam-dry over low heat for 1 minute. Pass hot vegetables through a potato ricer into a clean bowl.
Beat in the cold cubed butter until absorbed. Stream in the warm double cream, whisking until light, silky, and cloud-soft.
Season with nutmeg, white pepper, and sea salt, swirling into a warmed serving dish.