Scrub potatoes and sprinkle lightly with salt and bake in pan at 375 degrees for 1 1/4 to 1 1/2 hours. One same rack, cook yams wrapped in foil for 1 hour or until soft to touch. Remove from oven & slice potatoes in half, scoop insides into large bowl an put empty halves back into pan. Skin yams and put in a large bowl with potatoes. Beat with mixer on high while adding butter, sour cream and cheese. Add mile a little at a time until it gets to a lightly fluffy consistency. Don't add too much or it will get thick and sticky. Add sale and pepper to taste and scoop mixture into potato halves. Sprinkle top with parsley and grated romano or parmesan to garnish and bake at 350 degrees for 45 min.