Boil whole russet potatoes in their skins until they're easily pierced with a knife; let cool slightly before peeling. While the potatoes are boiling, saute sliced white onions in olive oil or butter over low heat until soft and deeply caramelized. Mash the potatoes with milk or cream, butter, and salt and pepper to taste. Stir the caramelized onions into the potatoes just before serving.
Photograph by Anita Calero