Trim crust from white bread; discard crust. Place bread in a large mixing bowl. Cover with water; let stand 15 minutes. Drain off water, and squeeze excess water from bread; return bread to large mixing bowl. Stir until doughy.
Place Cuban bread in container of an electric blender, a few slices at a time; process until breadcrumbs are fine. Repeat procedure with remaining toasted Cuban bread. Add breadcrumbs, paprika, if desired, and salt to white bread, mixing until soft dough forms. Cover and refrigerate dough until ready to use.
Note: 4 1/4 cups fine dry breadcrumbs may be substituted for 1-pound loaf of Cuban bread.