To prepare turnips for soup, peel and blanch them, and cut them to a medium dice or into strips. Bring them to a boil and simmer until soft, 30 to 45 minutes depending on how small the turnips are diced. Turnips soften at about the same speed as potatoes when boiled or simmered and more quickly than carrots and parsnips.
Peel a turnip by cutting off the top and bottom, and use a potato peeler to remove the skin. To blanch vegetables, bring a large pot of water to a rolling boil, and put the vegetables in for two to three minutes.
If you like vegetables crunchy or al dente, reduce the cooking time. When you simmer turnips for 45 minutes, they're soft enough to puree in a blender or food processor and are ready to make a smooth, creamy soup. Diced or chopped turnips can also be used in chicken soups, stews, tomato soups and as a healthy substitute for potatoes in most recipes. Turnips pair well with onions and leeks, and many soup recipes contain both. Onions or leeks are often sauteed in butter or olive oil for flavor before adding the water or stock and the turnips.