In a large bowl, combine all ingredients except olive oil.
Mix well and divide into quarters. Shape each quarter into a patty.
Heat a large pan over medium heat and spray with olive oil. Add the patties and cook until bottoms are browned, about 5 minutes. Turn and cook until the other side is brown and the burger is cooked through, another 5 minutes or so.
Serve burger with mustard sauce on a bed of greens or on toasted ciabatta.