This recipe comes from the Elms restaurant and tavern in Ridgefield, Connecticut, and makes an excellent accompaniment to our Perfect Roast Turkey.
Heat oven to 475 degrees. Wrap beets in aluminum foil. Bake until a knife easily pierces beets, about 45 minutes. Let cool 1 hour. Meanwhile, toss apples with lemon juice.
Bring a large stockpot of salted water to a boil. Meanwhile, prepare an ice-water bath. Blanch potato for 1 minute, and transfer to ice-water bath to stop cooking. Remove potato from bath; drain in colander. Repeat process for celery root and squash, blanching each for 2 minutes.
In a heavy skillet over medium-high heat, melt butter until bubbling. Add onion, and cook until softened, about 2 minutes. Add celery root, and cook 2 minutes. Add potato; cook 1 minute. Add beets and apples; cook, stirring, until all ingredients are tender, about 3 minutes. Season to taste.
Remove from heat; sprinkle with parsley. Serve.