In a large skillet, cook pork until no longer pink; drain and set aside.
In a large kettle or Dutch oven, cook cauliflower in water until tender, 10 minutes. Do not drain. Add pork, onion and 1-1/4 cups milk to cauliflower.
In a small bowl, combine flour and remaining milk until smooth; stir into cauliflower mixture. Bring to a boil; boil and stir for 2 minutes. Remove from the heat; add cheese, salt and pepper, stirring until cheese melts. If desired, sprinkle with chives.