cup butter, at room temperature
cup hot, unseasoned mashed potatoes
package active dry yeast (That would be 2-½ teaspoons for those using bulk yeast ... also available from King Arthur flour. I double this amount if I am in a hurry.)
cups warm milk
eggs, lightly beaten
cups all-purpose flour (enough to make a soft but manageable dough)
Combine butter, mashed potatoes, sugar and salt and stir until butter melts (if using leftover mashed potatoes, melt the butter and add it ... that warms up the potatoes). Cool mixture to 105 to 115 (or lukewarm). Sprinkle yeast over warm milk in a large mixing bowl (milk should feel comfortably warm when dropped on wrist). Stir until yeast dissolves.Add mashed-potato mixture to yeast; beat in eggs. Add the flour about 2 cups at a time, beating well to blend. Add only enough flour to give you a soft but workable dough -- it should not be so sticky that you cannot knead it. Turn dough onto a floured board and, with well-floured hands, knead about 5 minutes or until soft and springy (I do the mixing in my Kitchen Aid with the beater until it is "shaggy" and switch to a kneading hook for the kneading ... but for many years I made these by hand). Turn dough into a buttered bowl and brush the surface with melted butter. Cover with a clean dry cloth and let the dough rise in a warm, draft-free spot until doubled in bulk -- about 2 hours. (This dough takes somewhat longer than usual to rise because it contains only 1 package of yeast.) Punch dough down and let rest about 10 minutes. Turn onto a lightly floured board and knead lightly again -- about 2-3 minutes. Pinch off bits of dough and roll into balls about the size of golf balls. Arrange one layer deep, in concentric rings, in three well-greased 9-inch layer-cake pans (I also have used pie pans for this), spacing the rolls so that they do not quite touch one another (they will after they have risen). Cover pans with clean dry cloth, set in a warm, draft-free spot and again let rise until double in bulk -- about 1 hour or slightly longer. Bake the rolls in a very hot oven (450) for 10 minutes or until rolls are nicely browned and sound hollow when thumped with your fingers. Serve hot with plenty of butter.