In a glass bowl combine together the milk and the mustard. Season the shrimp with the onion powder and cayenne. Place the seasoned shrimp in the milk mixture. In another bowl, combine the corn meal and corn flour.
Dredge the shrimp with the corn meal and flour mixture and place in frying pan. (Oil is usually hot enough when a small pinch of flour dances on the surface of the oil). Fry until the shrimp float. Remove and place on paper towels to drain. To keep warm, preheat oven to 200 degrees. Place shrimp in oven until ready to eat.
Or for a heart healthy way to prepare - Place shrimp on a cookie sheet that has been covered with foil and sprayed with PAM or other cooking spray. Bake at 350 degrees for 12 to 15 minutes.