This is a hearty soup, but it's not heavy or greasy. I use chicken breasts for quick cooking, but you could extend the cooking time and sub in chicken thighs too. For added protein, I sometimes stir in some cooked white beans or chickpeas. If you have leftover cooked chicken, you can also build the soup and stir in the chicken at the last minute. Letting the soup cool slightly before eating can be key. We let steak and bread rest before eating them, so give your soup a few minutes to rest before digging in as well.
Start the soup: Heat a large soup pot over medium heat. Add the olive oil, scallions, carrots, garlic and mushrooms and season with salt and the oregano. Cook over medium high heat, stirring with a wooden spoon, until the vegetables become tender, 8 to 10 minutes. Add the chicken stock and tomatoes, bring to a simmer and cook for 5 minutes so the tomatoes lose their raw taste.
Cook the chicken and pasta: Season the chicken breasts with salt on all sides. Lower the heat and add the chicken breasts and elbow macaroni. Simmer until the pasta cooks and the chicken breasts are cooked through and register 160 degrees F on a meat thermometer, 8 to 10 minutes.
Finish: Turn off the heat. Using a slotted spoon, remove the chicken and transfer to a flat surface. Put a fork in each piece of chicken to hold it in place and avoid touching the hot meat with your hands as you cut. Slice the chicken into small pieces and add it back into the soup. Allow the soup to "stand" on the stove for 5 minutes before serving. Taste for seasoning. Stir in the basil and cheese.