"Rich, subtly spiced with cinnamon and ginger, and sweet with molasses, this dessert is a version of the pudding that has been served at the venerable Rhode Island clam shack Aunt Carrie's since it opened, in the 1920s." - Saveur
Heat oven to 350°F Grease an 8" × 8" baking dish; set aside.
Put 2 cups of the milk and 2 cups hot water into a medium pot and bring just to a boil. Slowly pour in cornmeal while whisking constantly. Reduce heat to medium and cook, whisking constantly, until very thick, 12-14 minutes.
Remove from heat and whisk in remaining butter. Set cornmeal mixture aside.
Whisk together molasses, flour, cinnamon, ginger, salt, and egg in a large bowl. Pour molasses mixture into cornmeal mixture while whisking constantly. Transfer batter to prepared baking dish; pour remaining milk evenly over batter.
Bake, rotating once, until pudding is set but still soft and a skin has formed over the top, about 1 hour. (If pudding gets too dark while baking, tent with foil.).
Set pudding aside to let cool to room temperature. Spoon pudding into bowls and top with scoops of vanilla ice cream.