Place the sliced tomatoes on a sheet tray with a rack and season them with salt and pepper. Bake them at 275° in the oven for 1 hour (see video). Set aside when done.
Next, Mix the ground turkey meat with all onions, garlic, mustard mayo, Worcestershire sauce, salt, and pepper until combined. Cover and set aside in the refrigerator until ready to start forming and cooking.
In the meantime, add the 1 tablespoons of butter to a large frying pan over medium heat and caramelize the red onions until browned, which takes about 10 to 15 minutes while frequently stirring. Deglaze with the balsamic vinegar, mix in, and set aside.
Make the chipotle mayo sauce and set to the side until ready to use.
Mash the avocado with lemon juice, salt, and pepper, using a hand masher until it resembles the consistency of guacamole. Keep cool to the side.
Heat a griddle or large cast iron skillet to medium-high heat and add 2 tablespoons of butter until melted and hot.
Form the turkey burgers into 8 large patties and add them to the griddle as soon as they are made (see video).
Cook for 5 to 6 minutes per side or until it reaches an internal temperature of 165°.
Add the mozzarella cheese to each burger with 2 to 3 minutes left in the cooking process.
Toast the brioche buns on the griddle until lightly browned and toasted.
Assemble the burger by layering on as followed: Bottom toasted bun, lettuce, tomato, avocado, onion, turkey burger, chipotle mayonnaise, and then the final toasted top bun.
Notes
Make-Ahead: These turkey burgers are meant to be eaten as soon as they are finished cooking. You can however prepare all the toppings 1 day ahead of time.How to Store: Keep the meat and toppings separate and covered in the refrigerator for up to 4 days. The turkey burgers by themselves will freeze well covered for up to 3 months. Thaw in the refrigerator for 1 day before reheating and serving.How to Reheat: Add the desired number of turkey burgers to a 13x9 casserole dish and cover with foil or a lid. Bake in the oven at 350° for 8-12 minutes or until warm.Feel free to use all turkey thigh meat in this recipe.If you aren’t a fan of turkey, this recipe will also work well if you substitute it with ground chicken.The toppings in this recipe are subjective, however, I feel they do a good job of complimenting flavors to make a very delicious turkey burger.