Bring the stock to a boil in a medium, heavy saucepan over medium high heat. Add the farro and reduce the heat to a simmer; cook until just tender, about 20 to 25 minutes. Drain the farro over a bowl so that you can reserve what's left of the cooking liquid, and set both aside.
Rinse the saucepan and add the butter and olive oil, setting it over medium-high heat. When the butter has melted, add the mushrooms and sauté until lightly browned, about 6 minutes. Reduce the heat to medium and add the onion, garlic, salt and black pepper and continue to cook until the onion is softened, about 3 minutes more.
Pour in the wine and continue to cook until the wine is almost evaporated, another 5 minutes or so.
Add the drained farro and cook for a couple of minutes, stirring occasionally, until heated through. Fold in the Parmesan, adding enough of the reserved chicken stock (about 1/4 cup) to get a slightly creamy consistency. Serve immediately, with more Parmesan on the side.
Nutrition information per serving:
Calories303Fat11 gSodium430 mg