Preheat oven to 350 degrees. Wash potatoes, cutting off any "eyes," and pierce potatoes with a fork in several places. Wrap in foil. Place on oven rack and bake for one hour, 15 minutes. Remove from oven, unwrap. When cooled enough to touch, remove skins and place in a pan or sturdy bowl. Mash with a large fork or with a potato masher.
To steam potatoes
Wash potatoes thoroughly, cutting off any "eyes," and place in a steamer over boiling water. Cover and cook until they easily break apart, 15 to 20 minutes. Remove from steamer and place in a pan or sturdy bowl. Mash with a large fork or with a potato masher.
While potatoes are cooking, thoroughly rinse anchovies, pat dry and mash (works well in a food processor).
In a saucepan over low heat, melt the butter, and add the onions, sauté until onions are soft but not browned. Stir in the anchovies and mix until dissolved, about one minute. Stir in the broth until well-mixed, then the cream.
Meanwhile, gently sauté onions over low heat in the butter until they are soft, but not browned. Stir in the anchovies and mash until they disintegrate into the onions. Stir in broth and cream. Heat but do not boil.
Add potatoes to the mixture stir together until preferred consistency. Serve sprinkled with parsley, salt and pepper to taste.