Combine butter, cream, salt, sugar, and sweet potatoes in 3 to 4 quart saucepan; cook, covered, over low heat, stirring occasionally, until potatoes fall apart when poked with fork, 35 to 45 minutes.
Off heat, mash sweet potatoes in saucepan with potato masher, or transfer mixture to hopper of food mill and process into warmed serving bowl. Stir in pepper, maple syrup, and orange zest; serve immediately.