Martha Stewart's Four-Root Puree

 Martha made this on the Today show with her honey mustard salmon see separate post. Very good and it would go with anything chicken or pork as well.

2½ pounds celeriac (1 very large or 2 smaller), peeled and cut into 1-inch pieces 

3 pounds russet potatoes or other starchy potatoes, peeled and cut into 1-inch pieces 

1 large parsnip, peeled and cut into 1-inch pieces 

4 large carrots, peeled and cut into 1-inch pieces 

kosher salt and freshly ground white pepper 

6 tablespoons unsalted butter  

Place each vegetable in its own pot. 

Cover with water by 1 inch. Add 1 teaspoon salt to each pot. 

Bring to a boil, reduce heat, and simmer until tender: 

10 to 15 minutes for celeriac and potatoes; 

10 to 12 minutes for parsnip and carrots.   

Drain all the vegetables, reserving 1 cup of the potato cooking liquid. 

Working in batches, puree the vegetablesin a food processor, adding the potato cooking liquid to create a smooth puree. Stir in the butter until the butter melts. Season with salt and white pepper. Serve hot. :