Heat 2 tablespoons olive oil in a large skillet over low heat. Add 2 bunches stemmed mustard greens and cook until wilted. Add 3/4 cup chicken broth and cook 15 to 20 minutes. Season with salt and pepper. Toss 1 chopped beefsteak tomato with olive oil and salt and pepper. Top the greens with the tomato and shaved cheddar.