From the blog For Love of the Table
5 T. unsalted butter
1 large or two small onions (about 10 oz.), cut in 1/4-inch dice (2 cups)
3 cloves garlic, peeled and minced
1 T. minced fresh thyme
5 c. diced (1/4- to 1/3-inch) root vegetables (see notes)
6 cups chicken stock (or more, if you prefer a soup with a greater proportion of broth)
1/2 c. pearled or semi-pearled farro, rinsed
4 to 5 oz. Brussels sprouts, trimmed, cored and thinly sliced (1 1/2 cups sliced)
2 T. coarsely chopped flat leaf parsley, optional
In a large soup pot over medium heat, melt butter. Add the onion along with a pinch of salt and sweat until very soft (about 15 minutes). Add the garlic and thyme and cook another minute or two, or until fragrant. Add the root vegetables and cook until hot and beginning to sizzle in the butter. Add the stock and bring to a boil. Taste and season with salt. Add the farro, return to a simmer, cover and simmer gently until the vegetables are almost tender—15 minutes. Add the sprouts, return to a simmer and cook until the farro is tender—another 10 minutes or so. If you would like a soup with a greater proportion of broth, simply add broth (or water) to obtain a soup that pleases you—I prefer a soup that is filled with vegetables that are snug, but moving freely in the broth. Taste and correct the seasoning. Serve sprinkled with minced parsley if desired.
Makes about 2 quarts of soup.
Notes &Variations:
As noted in my post, I simply used the root vegetables that I had on hand...1 large parsnip, 1 small (6 oz.) sweet potato, 1 medium kohlrabi, 1/2 a celeriac and 1 large carrot to round it out. But you could also use potato, turnip, rutabaga (swede), or winter squash. I would limit the variety of root vegetables to 3 to 5 different kinds.
If you like...and you have it on hand...a couple of leeks would be a delicious substitution for the onion.
Cabbage would be a fine substitute for the Brussels sprouts. Cut it small squares to mirror the other vegetable shapes. Or, follow Joanne Weir's lead and use chopped (small) broccoli tips instead of cabbage. If you use broccoli, peel and dice the stems and use them as part of your volume of "root vegetables"...adding them to the soup when you add the root vegetables.
http://www.forloveofthetable.com/2014/03/end-of-winter-vegetable-soup-with-farro.html