• Prepare all of the burger toppings and set aside.
• Prepare the saganaki cheese ingredients by slicing the cheese, measuring out the flour, olive oil, brandy or bourbon and setting aside.
• Make the burger patties: In a mixing bowl combine the ground beef, grated onion, grated tomato and their juices, egg, breadcrumbs, olive oil, parsley, salt and pepper.
• Mix together to fully combine. Divide the mixture into 10 portions and use your hands to form into balls.
• Preheat the flat-top to medium-high heat.
• When the flat top is ready, oil the flat top with a bit of olive oil if desired. Working with one ball of meat at a time, place on the grill and smash the ball flat with a spatula until all of the burgers are on the grill. Cook each smash burger for 3-4 minutes, flip and cook for 3-4 more. Remove the burgers from the grill and set aside.
• After the burgers come off the grill, let them rest while you toast the buns on the grill.

Once the buns are toasted, make the saganaki cheese for the burgers -

• Brush each side of one cheese slice with water or run quickly under water. Then, dredge in the flour, shaking off excess flour.
• Place a cast iron skillet or heavy-bottomed skillet over medium-high heat until hot and then turn the heat to medium. Pour in 1 tbsp olive oil.
• Add cheese to the hot pan and cook until the cheese just begins to melt and a golden brown crust forms, about 2 minutes. Quickly flip the cheese and cook another 1-2 minutes until golden brown on the other side.
• Remove the skillet from the heat immediately and place on a wooden cutting board. You can skip this next step if you'd like to serve right away.
• Make sure you have a lot of space above the pan as the flame can get quite high. Pour 2 tbsp bourbon or brandy over the cheese in the skillet and then light the bourbon using a long lighter so you can stand as far away from the pan for safety. Squeeze some lemon juice over top after the flames extinguish (you can gently blow on the flame to help it extinguish).
• Repeat until you have 4 melted cheese slices.
• Assemble the burgers by slathering the bottom of each bun with tzatziki and then stacking as follows: lettuce, tomato slice, burger patty, burger patty, slice of saganaki cheese and round of onion.
• and enjoy!