The best mushrooms for this dish are chanterelles. Hedgehog, cauliflower and oyster mushrooms work, well, too. Do not, however, use shiitakes; they have a distinct flavor that is doesn't work in this dish. In a pinch, use portobellos, but be sure and simmer to reduce the pan juices, as portobellos typically release more liquid than wild mushrooms.
Put the farro into a medium saucepan, add water to cover it by two inches, pour in 2 teaspoons of salt and bring to a boil over high heat. Reduce the heat to low and simmer gently until the farro is tender, about 40 minutes.
Meanwhile, fry the bacon in a heavy skillet set over medium heat until it is crisp, transfer to absorbent paper and let it drain. Set aside.
Clean the mushrooms, brushing off any soil; break them into large bite-size pieces. Set aside.
Pour off the bacon fat, leaving any bits of bacon and a some of the fat in the pan. Put 2 tablespoons of the butter in the pan, reduce the heat to low and when the butter is melted, add the shallots. Cook slowly until soft and fragrant, about 8 to 10 minutes. Add the garlic, saute two minutes more and season with salt.
Add 1 tablespoon of the remaining butter to the pan and when it is melted, add the cleaned mushrooms, the white wine and the thyme sprigs. Increase the heat to medium and when the liquid boils, cover the pan, reduce the heat to low and cook until the mushrooms are tender. Add 1 tablespoon of the remaining butter to the pan and when it is melted, add the cleaned mushrooms, the white wine and the thyme sprigs. Increase the heat to medium and when the liquid boils, cover the pan, reduce the heat to low and cook until the mushrooms are tender. Check the mushrooms after 5 minutes; it can take as long as 20 minutes, depending on the type of mushroom used.
When the mushrooms are fully tender, uncover the pan and simmer to thicken the juices. Use tongs to remove and discard the thyme sprigs.
Crush or chop the bacon and fold it into the mushrooms.
Taste, correct for salt and season with several generous turns of black pepper.
Drain off any water that remains with the farro and spoon the farro into individual soup plates. Top with mushroom ragout, sprinkle with herbs and serve.