Instructions

1. 1
   Preheat oven to 250°F and a grill or grill pan to 350°F.
2. 2
   Toast buns in hot oven. Set aside.
3. 3
   Combine salt, pepper, garlic powder, and rosemary. Set aside.
4. 4
   Combine chuck and sirloin, and place on a parchment-lined sheet pan. Cover with a sheet of plastic wrap and roll out until the meat fills the pan.
5. 5
   Remove plastic and, using a pizza cutter or wheel, cut into 16 equal squares.
6. 6
   Brush patties with olive oil and season on both sides with seasoning mixture.
7. 7
   Cook patties on the preheated grill for 2–3 minutes per side.
8. 8
   Spread buns with mayonnaise. Place a patty on top of a bun half and top with the other half. Serve warm.