Add the olive oil and onion to a large soup pot over medium-high heat. Sauté for 5 minutes.
Meanwhile, chop the mushrooms and carrots.
Add the mushrooms and garlic to the pot and sauté for another 5 minutes.
Add the carrots, Italian seasoning, chicken broth, and water to the pot. Increase the heat to high and bring to a gentle boil.
Add the pasta and chicken to the pot. Reduce the heat to medium and simmer for 10 minutes, stirring occasionally so the pasta doesn't stick to the bottom of the pot.
Add the half-and-half and salt & pepper. Cook for another 5 minutes. The carrots should be cooked by now, but if they're not, give it another few minutes.