Preheat oven to 375 degrees. Melt butter in large skillet over medium heat; add sausage, green pepper and onion. Cook, stirring occasionally, 5 to 6 minutes or until vegetables are tender.
Slice potaotes in half lengthwise. Scoop potato out of each half, leaving a 1/4 inch thick shell. Combine potato pulp, sour cream, milk, salt and black pepper in large bowl, mashing until smooth. Stir in sausage mixture, cheese and chives. Spoon mashed potato mixture into potato shells.
Place filled potato shells on large baking pan. Bake 30 minutes or until tops are lightly browned and filling is hot.