Preheat oven to 450°F. (225°C).
Wash potatoes and pat dry.
Rub potato skins with oil and prick several times.
Place in hot oven for 45 to 60 minutes or until tender.
Cut potatoes in half and scoop out pulp.
Do not break the skins.
Mash pulp well.
Add sour cream and milk.
Beat until smooth.
Stir in cheese, setting aside enough for the garnish.
Add parsley, salt and pepper.
Place mashed potato mixture back in potato shells, mounding slightly.
Dot each potato with butter.
Return to oven for 10 minutes.
Garnish with chopped chives and reserved Roquefort cheese.