Add cool water to cover, bring to a boil, then reduce the heat to simmer until the potatoes are tender, about 20 minutes. Drain and mash or rice the potatoes into a bowl and mix in:
3 tablespoons butter, softened
½ cup grated sharp Cheddar or Parmesan (2 ounces)
(½ small onion, minced and sautéed)
Salt and black pepper to taste
Allow to cool completely before using.
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