Sift together the dry ingredients. Add the cranberries, milk, melted butter and vanilla. Mix well. Pour into an 8 inch square buttered baking dish.
Bake at 350° for 40 minutes.
After the duff has been in the oven for 25 minutes, make the butter sauce by combining the butter, sugar and cream in a heavy-bottomed saucepan. Bring to a boil and then lower the heat. Stir in the vanilla and cinnamon and simmer for 10 minutes.
Serve warm drizzled with the sauce, with extra sauce on the side. Enjoy!