Grate onion with a box grater and put into a medium bowl.
Add turkey, bread crumbs, cheddar, dijon, salt and pepper and mix well.
Using damp hands, take about ¼ cup of turkey mixture and make small, equal size patties and place on clean plate. You should have about 9 mini burgers.
Mix all the sauce ingredients together and set aside.
Heat 2 tablespoons oil in a large skillet or grill pan over medium heat. Once sizzling, add the turkey patties and cook until done, about 3-4 minutes on each side (2-3 if using beef)
Cut the buns in half and lightly toast. Place one turkey patty on each bun and top with 1 tablespoon sauce, lettuce, onion and/or avocado.
**Alternatively, you can use romaine leaves as buns for a gluten free version.
Serve with sweet potato fries.
Recipe by Three Hungry Boys at https://www.threehungryboys.com/2016/08/31/mini-turkey-burgers/