Return medium pot to stove over high heat. Add 1 Tbsp. olive oil into hot pot. Add cremini mushrooms and cook until lightly browned, about 3 minutes. Reduce heat to medium-high and add carrots, shallots, and a pinch of salt and pepper. Cook 2 minutes, add barley and 2 cups water. Bring to a boil, reduce to a simmer, cover, and cook about 25 minutes, or until liquid has been absorbed and barley and carrots are tender. Season with salt and pepper to taste. Set aside.