Melt the butter in a medium skillet over medium-high heat

Add the mushrooms, green onions and garlic and cook until mushrooms are lightly browned

Season to taste with salt and pepper

Set aside to cool to room temperature. Divide ground beef and form into 8 patties

Divide the mushroom mixture evenly into quarters and place on 4 of the patties

Top with remaining 4 patties and press to seal the edges

Season the outside well with salt and pepper. Rotate in the Flat Standard Basket for 20 minutes for medium-well or until cooked to desired doneness

If not brown enough, position the basket facing the heating coils and push the switch to the pause-to-sear position

Rotate 2 to 3 minutes more on each side.