Preheat the oven to 400 degrees F. Spray an 8-inch square baking dish with cooking spray.
On a foil-covered baking sheet, bake the sweet potatoes until soft, about 1 hour. Remove and let cool. Reduce the oven temperature to 325 degrees F. When cool enough to handle, peel the potatoes, place the flesh in a large mixing bowl, add the butter and mash until smooth. Add the eggs 1 at a time, beating well after each addition. Add the sugar, milk, cornmeal, salt and 1/2 teaspoon of the vanilla and beat until smooth. Pour the batter into the prepared baking dish. Arrange the pecan halves on top of the pudding and top with the brown sugar. Sprinkle the remaining 1/2 teaspoon vanilla by small droplets over the brown sugar. Bake until the top is browned, about 45 minutes.
You could add whipped cream and serve for dessert!