Preheat oven to 375 degrees F. Place potato in a Dutch oven, and cover with water. Bring to a boil. Reduce heat; simmer 12 minutes or until tender. Drain.
Combine the half-and-half and next 4 ingredients (half-and-half through egg) in a large bowl, stirring with a whisk. Add potato to egg mixture; beat with a mixer at medium speed until smooth. Spoon potato mixture into a 13 x 9-inch baking dish coated with cooking spray.
Combine flour and sugar in a food processor; pulse to combine. Add chilled butter; pulse until mixture resembles coarse meal. Stir in pecans; sprinkle over potato mixture.
Cover and bake for 15 minutes. Uncover and bake an additional 25 minutes or until the topping is browned and the potatoes are thoroughly heated.