Heat a grill or grill pan to medium high heat. Spray with olive oil or cooking spray.
Combine all ingredients excluding the spinach and Dijon mustard. Form 6 patties. Place patties on grill/grill pan.
Cook patties about 5-6 minutes per side or until internal temp reads 165F. Spread with dijon mustard and top with spinach leaves. Add other toppings as desired.