I cannot think of a single decent-tasting use for breadcrumbs that are made with the crusts left on. Not one, since when they are left on and cooked (again), the resulting flavor is so strong that they overpower anything, even mustard.
Put the bread cubes in a food processor or blender to make the crumbs. Leave out on a tray to become stale if that is what the recipe calls for. Otherwise transfer to a sealed jar and freeze for up to a month.