Preheat oven to 400 degrees F (200 degrees C). Lightly grease a medium casserole dish.
Place potatoes in a pot with enough water to cover, and bring to a boil. Cook 10 minutes, or until tender but firm. Cool, and partially mash together with 3/4 cup Parmesan cheese and 1/2 cup sour cream. Set aside.
Place sun-dried tomatoes, butter, spinach, garlic, and remaining 1/4 cup Parmesan cheese in a blender or food processor, and blend until almost smooth.
Heat the olive oil in a skillet over medium heat, and cook the onion and green bell pepper until tender. Reserve remaining oil in skillet, and spread onion and pepper over the bottom of the casserole dish. Top with the potato mixture.
Mix the sun-dried tomato mixture into the skillet with the remaining oil.
Place chicken in skillet, and cook 4 minutes on each side over medium heat, until browned and juices run clear. Arrange chicken and sun-dried tomato mixture over the potato mixture in the casserole dish, and top with remaining 1 cup sour cream.
Bake 15 minutes in the preheated oven, until lightly browned.
