I have been making this soup for years. And everyone loves this soup.You don’t need to worry too much about exact quantities here. Just use the root vegetables you have around. Full Plate CSA has been supplying us with great amounts of parsnips, turnips, rutabagas and carrots. I also love celeriac in this soup, and butternut squash. 
2 Tbs. butter
1-2 Tbs. olive oil
1 medium onion, chopped
½ pound of at least three of the following: parsnips, carrots, rutabaga, butternut and celeriac, or turnips peeled and cut into about a ¾   inch dice.
32 ounces of either chicken or vegetable
1 bay leaf
Salt and pepper to taste
¼ cup water
1-2 Tbs. corn starch
½ cup milk or ½ and ½ or cream
Salt and pepper to taste
1 cup frozen green peas
  1. Fry onions in 1 tbs. melted butter in large saucepan until soft and just beginning to brown, remove and set aside.
  2. Add the rest of the butter and some olive oil and fry the vegetables one vegetable at a time over very high heat until fragrant and beginning to brown. 
  3. Combine  all the vegetables including the onions, add a bay leaf and salt and pepper to taste, and the broth and simmer, covered for 20-30 minutes or until the vegetables are soft, but not mushy.
  4. Just before the vegetables are cooked mix the cornstarch and water together and add 1 tablespoon at a time, stirring to the soup. Let it cook together and add only as much cornstarch as necessary to make a chowder consistency, stirring to avoid lumps. Simmer gently until the cornstarch taste is gone.
  5. Remove from heat and for best results refrigerate at least a day.
  6. Reheat, and when simmering add frozen peas. 
  7. When the peas are cooked, add the milk and remove the bay leaf.
  8. Taste for seasoning. This soup is good with lots of pepper.