White Bean and Barley Soup With Tomatoes and Greens

Name: White Bean and Barley Soup With Tomatoes and Greens
Ingredients: 3 tablespoons olive oil, plus more for serving; 1 large onion, chopped; 3 cloves garlic, chopped; Kosher salt and black pepper; 6 cups low-sodium vegetable broth; 1 28-ounce can whole peeled tomatoes, crushed; 1 cup pearl barley, rinsed; 1 small bunch collard greens or kale, stems discarded and leaves cut into strips (4 cups); 1 15-ounce can cannellini beans, rinsed; ½ cup finely grated Parmesan (about 2 ounces), plus more for serving