1In a large pot, melt the butter and add the onion, garlic, celery and carrots. Saute, stirring often, for 3-4 minutes, until the veggies are slightly tender and the onions are translucent. Add the chicken broth and potatoes. Bring the soup to a simmer and cook, partially covered, until the potatoes are tender, about 10 minutes. In a liquid measuring cup, vigorously whisk the flour and milk together until smooth. Whisk the mixture into the soup, stirring quickly, and cook over medium heat for 3-4 minutes, until the soup begins to thicken slightly. Stir often to ensure the soup doesn't burn. Soften the cream cheese in the microwave until it is very soft/melty. I usually place the unwrapped cream cheese on a plate and microwave it for one minute at 30% power. I like it really, really soft so it doesn't leave lumps in the soup. Add the cream cheese to the soup in small tablespoon-size pieces. Let the pieces sit in the soup and warm through then whisk or stir the soup until the cream cheese melts and mixes in well. Add the cooked chicken and heat through. Season with salt and pepper. Serve.