1Use a meat tenderizer to pound out the chicken breasts until about ¼-inch thick.
2Heat olive oil in a heavy skillet over medium-high heat. Saute mushrooms, bell pepper, and onions for 5 minutes, until par-cooked.
3Preheat oven to 400 degrees. Lightly grease a 9x13 pan.
4Place a pinch of cheese in the center of each chicken breast. Place a large spoonful of mushroom and bell pepper mixture on top. Finish off with another pinch of cheese
5Carefully roll up the chicken so stuffing is completely inside. Secure the chicken with toothpicks. Place in the prepared pan. Season generously with cajun seasoning. Place a tablespoon of butter on top of each chicken breast.
6Bake in the preheated oven until chicken is cooked through, to an internal temperature of 165 degrees, about 30 to 40 minutes.
7Remove toothpicks before serving. You can serve the chicken whole, or slice in half, or in 1-inch slices.