½ cup finely grated Parmigiano cheese, plus more for garnish
For the Roasted Mushrooms:
1 ½ pounds mixed mushrooms (oyster, hon shimeji, shiitake, baby bella), trimmed and sliced (about 5 cups)
3 tablespoons extra virgin olive oil, plus more for drizzling
2 tablespoons chopped fresh thyme, plus more for garnish
1 teaspoon kosher salt
½ teaspoon freshly ground black pepper
Make the Risotto: Preheat the oven to 350°F. Arrange one rack in the lower third of the oven and one in the center (one will hold the roasting mushrooms and one will hold your risotto saucepan).Bring the broth to a boil in a small saucepan, throw in the porcinis, cover, turn off the heat, and let it sit while you prep everything else
Heat the butter and olive oil in a medium, oven-safe saucepan (make sure it has a tight-fitting lid) over medium heat. Add the shallots and garlic and cook, stirring, until translucent and fragrant, 3 to 4 minutes. Add the barley and thyme sprigs and cook, stirring, until the barley is shiny and coated in oil, 2 to 3 minutes. Strain the broth into the barley (it will sputter a bit), then finely chop the porcinis, add them to the barley and broth along with the salt and pepper. Cover while still boiling and transfer to the middle oven rack. Bake until the barley has absorbed the liquid and is tender, 40 to 45 minutes.
Make the Roasted Mushrooms: During the last 30 minutes of the risotto cooking, toss the sliced mushrooms with the olive oil, thyme, salt, and pepper. Arrange them in an even layer on a rimmed baking sheet, slide the sheet into the bottom rack, and roast until the mushrooms wilt and some of the edges char, 30 minutes. Remove from the oven.
Carefully remove the risotto from the oven, uncover the pot, and discard the thyme sprigs. Stir in the Parm and season with more salt and pepper if needed. Divide among bowls, then spoon the roasted mushrooms on top of the bowls. Garnish with more cheese, thyme, and a drizzle of olive oi