Season chicken pieces with salt and pepper. Saute with olive oil for about 4-5 minutes while stirring in a medium sized pot. Place mushrooms over the chicken, and then the cubanelle pepers over the mushrooms. Arrange the tomato slices over the top side by side, don't leave empty spaces. Sprinkle crushed pepper paste all over tomatoes. Put the butter pieces over the tomatoes, close the lid. Turn the heat to high first. When the dish starts to boil, turn the heat down to medium-low heat. Cook for about 1 hr and 30 minutes.