Butter a 9-by-14-inch broiler-proof baking dish.
Cut out the blemishes or imperfections from the potatoes. Quarter the potatoes, add them to large pot with salted water to cover and boil until soft, 25 to 30 minutes.
Mash the potatoes, transfer them to a large bowl and cool in the refrigerator for 30 minutes.
Meanwhile, heat the cream, milk and 1 stick of the butter in a stock pot until warm. Add the polenta and 1 teaspoon of salt and cook over medium heat, stirring continuously to prevent clumping, until smooth and creamy, 50 to 60 minutes.
Stir the pepper and remaining stick of butter into the polenta. Add the polenta to the mashed potatoes and stir until thoroughly combined.
Transfer the polenta mixture to the prepared baking dish and spread it into an even layer.
Preheat the broiler. Broil the polenta mixture until the top of the dish has browned, 12 to 15 minutes. Serve immediately.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.