Potato & Celery Root Puree

1 pound celery root (celeriac), peeled, cut into 1-inch pieces

1 1/2 pounds russet potatoes, peeled, cut into 1-inch pieces

Salt

1/4 cup whipping cream

2 tablespoons (1/4 stick) butter

Place celery root and potatoes in large saucepan. Cover with water; salt lightly. Boil until very tender, about 15 minutes. Drain vegetables, reserving 1/4 cup liquid. Add vegetables to a kitchen aid or bowl with hand mixer. Add cream and butter and mix on high speed until silky smooth. Add cooking liquid if mixture become to thick. Season salt and pepper.