In Denmark, the regional rye bread, called rugbrød, is debatably sacred. Many bakeries stock upwards of five or six varieties of the nutty, rich, nutritious loaves. And when crumbs fall off while slicing it for smørrebrød, they're not tossed. They're saved (and soaked in beer) for this tangy, earthy breakfast treat.
Note: This recipe comes together quickly, but does need some advance planning. Make sure to soak the bread cubes the night before to make sure they hydrate completely.