Make the tzatziki sauce by mixing Greek yogurt, 2 minced garlic cloves, chopped chives, lemon juice together. Add salt & pepper to taste, and let sit in the fridge.
In a bowl, combine ground beef, chopped parsley, feta cheese, oregano, crushed red pepper, 2 minced garlic cloves until just combined. Be careful to not over mix, and don’t add salt yet!
Form into 4 patties and set aside on a plate. Heat a large skillet over medium heat for 5 mins.
Add 1-2 tbsp of oil to the pan and allow to heat for another 30 seconds.
Add burgers to the skillet and give a generous pinch of salt to each pattie. Sear on both sides for about 3 minutes, until cooked through.
Toast the buns face down in a pan until golden. Slather homemade tzatziki on both sides and top with burger, sliced red onion, tomatoes & butter lettuce.