1 tablespoon olive oil
3 tablespoons unsalted butter
1 cup pearled barley
1 strip fresh lemon zest
6 sprigs fresh thyme
2 1/4 cups chicken stock
3 tablespoons chopped fresh flat-leaf parsley, plus whole leaves, for garnish
1 small yellow onion, diced
8 ounces any combination of cremini, shiitake, or oyster mushrooms (about 4 cups)
4 tablespoons grated Parmesan (about 3/4 ounce)
Kosher salt