Preheat oven to 400°. Line baking sheet with foil. Rub the potatoes with oil; place on the baking sheet and bake for 1 hour, or until tender. Let cool enough to be able to handle. In a large skillet, melt butter over medium heat. Add chopped sage and garlic; cook, stirring often, until butter is browned and garlic tender, 5-6 minutes.

Peel potatoes; place pulp in a bowl. Add butter mixture, cream, S&P. Using a potato masher, mashed potatoes to desired consistency. Transfer to a serving bowl. Garnish with sage leaves if desired.