Salt, to taste (1 teaspoon is a good start), fresh pepper
Garnish: chopped fresh herbs such as parsley or chives
Peel the turnips, and dice them into 1 inch cubes. Scrub or peel the potatoes, and dice into 1 inch cubes.
Saute the onion in a large soup pot for 5 minutes, or until it softens. Try not to let it brown. Add the turnips, potatoes, vegetable stock, water, and nutmeg. Bring to a boil, then lower to heat and let it simmer for about 15 minutes, or until the potatoes and turnips are fully cooked.
Remove from heat and allow to cool for a while, so you don't burn yourself when blending this soup. Use an immersion blender to puree this soup to a desired consistency - you can leave a few chunks if you want. Taste the soup and season with additional salt and pepper, if desired. Serve hot with fresh herbs for garnish.
If you don't have an immersion blender, puree the soup in batches in a regular blender or a food processor. Just be careful not to burn yourself while pouring the soup back and forth!