Super Grain Soup with Watercress and Mushrooms

Heat oil in a pot over medium-high. When it shimmers, add mushrooms and onion; season with salt and pepper. Cook, stirring occasionally, until tender and golden brown in places, 10 to 12 minutes. Add grains and cook, stirring a few times, until toasted and nutty, 2 to 3 minutes.
Add broth; bring to a boil, then reduce heat to medium-low and simmer until grains are just cooked, 12 to 15 minutes. Remove from heat. Stir in Pecorino and lemon juice; season with salt and pepper. Serve with watercress, a drizzle of oil, more cheese, and lemon wedges.

Ingredient :

3 tablespoons extra-virgin olive oil, plus more for drizzling
8 ounces gourmet mushroom blend, thinly sliced (2 cups)
1 cup thinly sliced red onion (from 1 small)
Kosher salt and freshly ground pepper
1 cup super-grain blend or tricolor quinoa
6 cups low-sodium vegetable or chicken broth
½ cup grated Pecorino Romano Cheese, plus more for serving
2 tablespoons fresh lemon juice, plus wedges for serving
1 bunch watercress (3 ounces), trimmed and coarsely choppe