Add the stock, farro, and cauliflower to a large pasta pot off the heat. Let the farro soak while you prepare the onions and garlic.
Peel the onions, cut them in half, then slice them up and add them to the pot. Peel the garlic, cut off the root ends, and slice the garlic thinly. Add the garlic to the pot.
Stir in the tomato paste, olive oil, salt and red pepper flakes. Cover the pot and put the heat on high until the stock comes to a boil. When it is boiling, remove the cover, lower the heat until the pot is simmering gently. Set a timer for 25 minutes. Stir the pot occasionally to prevent sticking.
After 25 minutes, see if the farro needs more liquid added. (See notes. If the liquid has absorbed, add 1-2 cups of hot water as needed.) Simmer the farro for another 10 minutes, or until al dente and chewy. Turn off the heat. Do not drain any excess liquid.
Stir in ⅓ cup of Parmesan, if using. Taste to see if additional salt is needed. (It will depend on the stock you used.)
Serve the Italian farro with extra olive oil drizzled on top. Add ribbons of basil (roll the basil leaves the long way and snip them into pieces with scissors.) Serve with Parmesan on the side, if desired. Store leftovers in the refrigerator for up to 4 days or freeze them.
Notes
There are three kinds of farro: whole grain, semi-perlato, and pearled, with the highest nutritional value being in the whole version, and the least amount in the pearled, although that's still a good option. Whole-grain farro requires overnight soaking and a longer cooking time, so don't use it in this recipe. I usually use semi-pearled farro in this recipe, and don't need to add any more liquid than the 4 cups stated. When I recently made this with pearled farro, it absorbed all the liquid after 25 minutes but still needed more cooking. I added two cups of hot water and let it cook for another 10 minutes.To make this a vegan farro recipe, omit the cheese and use vegetable stock or water.For a vegetarian option, use vegetable stock or water instead of chicken stock.