Heat a small skillet and add the olive oil. Sauté the onion and garlic until they are soft and fragrant. Remove from heat and cool.
Using your hands, mix the meat, vegetables and seasoning together. Divide the mixture into five patties.
Heat a cast iron skillet or other heavy sauté pan. When it’s very hot, put the butter in the pan to keep the burgers from sticking. Sear the burgers on both sides, and put into the preheated oven to finish cooking -- for about 8 minutes.
Let the burgers rest for about 5 minutes before serving on toasted buns.