Slice peeled mangoes to make two cupsful packed hard into measuring cup. Melt three tablespoons butter and add the bread crumbs.
Sprinkle a layer of the buttered bread crumbs into an oiled baking dish, and place on top a layer of mango. Sprinkle the fruit with sugar to which one teaspoon of cinnamon has been added. Add another layer of bread crumbs, then a layer of mango, and top with crumbs.
Bake at 350 degrees for about one hour or until the mangoes are soft.