Whilst I appreciate that, for reasons best known to chefs, burgers are currently "on trend". May I suggest that if you must serve burgers in your restaurants, for heavens sake don't sandwich them between sour dough slabs, ciabatta or the equivalent of a loaf of bread.
These add nothing other than unnecessary stodge to what is in effect a lazy effort by the chef. Just use a bog standard hamburger bun.
Better still, stop being lazy and cook something more imaginative!