Bring a medium saucepan of salted water to a boil. Add the farro and cook until just tender, about 25 minutes. Drain and set aside.

Using the same saucepan over medium heat, add 1 tablespoon olive oil and saute the cauliflower just until tender, about 10 minutes. Add to bowl and set aside. Add 1 tablespoon olive oil the saucepan and saute the mushrooms for about 15 minutes or until browned. Transfer to the cauliflower bowl.

In a medium bowl whisk the vinegar and the remaining 1 tablespoon olive oil and the mustard. Add the farro, scallions, cauliflower, and mushrooms. Season with salt and freshly ground pepper to taste, stir to combine.