A variation on Mash Potatoes, the addition of celery root gives these potatoes a sweet taste of celery, not over powering the creamy Yukon potato.
In a large dutch oven or pot over medium heat, add quartered potatoes and chopped celery root (1). Top off with cold water to cover the root vegetables by an inch or so, seasoning water with salt to taste. Bring to a boil and cook for 30 minutes, or the potatoes and celery root are fork tender. Drain into a colander. Using a potato ricer (2) or spaetzle machine, press the potatoes and celery root into a bowl (3); creating a fine purée (4). If you do not have either device, a potato masher or fork will also work, resulting in a chunkier final product. Warm the milk and butter together in small pan. Add the milk/butter mixture to the potato/celery root puree and season with salt and pepper.