Fire up the BBQ to about medium heat. Place lid on BBQ to retain heat and let it warm up.

In a large bowl combine the meat, salt, pepper, paprika, red pepper flakes, and garlic. Using you hand, mix everything together until evenly distributed. Divide mixture into 4 sections and form into patties.

Remove the avocado from the skin and smash together with the chives and lime juice with a fork. Set aside.

Transfer patties to the heated grill and grill for about 5 minutes on each side until medium done. Add the cheese at the last minute and let slightly melt. Remove patties from grill and place on buns, top with guacamole and tomatoes if desired and serve.