1) In a large stockpot, bring the chicken stock, lemon juice, bay leaf and Parmesan rind, if using, to a boil over medium-high heat.
2) Add the carrots and simmer until tender, about 5 to 8 minutes.
3) Add the broken pasta and cook until the pasta's tender, for 4 to 5 minutes, stirring occasionally. Add the chicken and heat through, about 2 to 3 minutes. Remove the bay leaf and the Parmesan rind and discard. Stir in half of the cheese and the parsley. Season with salt, to taste.
Ladle the soup into serving bowls and sprinkle with the remaining cheese.
Cook's note: You can use any short pasta from your pantry as a substitute for spaghetti.