Heat a large frypan over medium-high heat. Cook mince and chicken with the Cajun seasoning until the meat is about halfway done. Add the margarine, mushrooms, spring onion, green capsicum and red capsicum. Saute over medium heat until the mushrooms begin to shrink, about 10 minutes.
Stir in the chicken stock and milk, season with lemon pepper and garlic powder and reduce the heat to medium-low. (Now is a good time to start boiling water for the pasta.) Mix together the cornflour and cold water until dissolved. Stir into the frypan. Cook, stirring gently, until the sauce returns to a boil. Boil for one minute then remove from heat and set aside.
Place pasta in a large pot of lightly salted water. Boil for 8 to 10 minutes, or until pasta is al dente. Drain. Serve with the sauce.