Put the turkey mince, herbs and mayonnaise in a large bowl and mix until well combined. Add the breadcrumbs, season with salt and pepper and mix again so the breadcrumbs are evenly distributed.
Split the mixture into 5 evenly sized balls and flatten to make a burger shape. Place a small slice of mozzarella on top, close the mince mixture over the cheese and reform into a burger shape with the cheese in the centre.
Chill in the fridge for at least 30 minutes before cooking.
Grill or BBQ the burgers for 5-6 minutes on each side until cooked through and serve on ciabatta with salad and relish.