Heat the oven to 350°F.
Place the potatoes into a 3-quart saucepan and add water to cover. Heat over medium-high heat to a boil. Reduce the heat to low. Cover and cook for 10 minutes or until the potatoes are tender. Drain the potatoes well in a colander.
Place the potatoes and heavy cream into a large bowl. Beat with an electric mixer on medium speed until the mixture is fluffy. Beat in the soup, brown sugar, eggs, vanilla extract, cinnamon and nutmeg. Pour the potato mixture into the pie crust and place onto a baking sheet.
Bake for 1 hour or until set. Let the pie cool in the pan on a wire rack for 3 hours.
Time-Saving: Substitute 1 3/4 cups drained and mashed canned sweet potatoes for the fresh mashed sweet potatoes.