1. Cover the dried porcini with 1/2 cup of recently boiled water, then fill the kettle and put it on the heat again if you are making up the broth with concentrate, cube, or powder. In a wide, heavy saucepan (that comes with a lid) add 2 tablespoons of the oil and the fine jade tangle of leek, and cook, stirring frequently, for about 5 minutes or until the leeks are softened.
2. Drain the porcini, reserving the soaking liquid, then chop them and add them to the pan. Stir well, then add the farro and turn it gently but thoroughly in the pan. Tip in the Marsala and porcini-soaking water and let it bubble up.
3. Make up the broth as wished and add this to the farro pan, stir, bring to a boil, and then clamp on a lid, turn down the heat, and let it cook at a simmer for 30 minutes, until the farro is cooked and all the liquid absorbed.
4. While the farro is cooking, warm the remaining 2 tablespoons oil in a medium-sized frying pan and cook the sliced crimini mushrooms for about 5 minutes or until they begin to soften (they will first seem alarmingly dry) at which point add the thyme, grate in (or mince and add) the garlic, and cook for a further 5 minutes or until the mushrooms are juicy and soft. Remove from the heat if there is still time on the clock for the farro. Once the farro is cooked, take it off the heat, too, and add the cooked mushrooms. Stir in the ricotta and Parmesan (they will melt in the heat of the farro) until the farro is creamy, then sprinkle with parsley and serve.