Place chicken in a saucepan, add water and bring to a boil. Simmer for 20 minutes. Take chicken out of the water and set aside.
While the water in the saucepan is still boiling, add the macaroni. Simmer for 10-12 minutes, adding in the carrots and celery in the last 5 minutes.
While waiting for the macaroni to cook, cut the chicken into cubes or tear into shreds using two forks.
In a heavy frypan, sauté the garlic, onion, sausage and chicken in oil. When the sausage and chicken have slightly browned, add the red capsicum and sauté all the ingredients in the frypan together for another minute.
Transfer all the ingredients in the frypan carefully into the saucepan. Add milk and stir. Add salt and pepper to taste. For more flavor, add one chicken stock cube and stir until dissolved.
Since milk curdles easily, you can choose not to mix in the milk while cooking and add it per serving instead.