1 ½cupsshredded Swiss cheeseor sharp white cheddar, divided
Instructions
To keep the sandwiches warm between batches, preheat the oven to 200°F.
In a large bowl, place the beef, oil, Worcestershire, onion powder, ½ teaspoon salt, and the pepper. With your hands, gently combine. Divide meat into thirds and shape into 3 oval patties that are each about 6 inches at their longest part and x 4 inches across the center.
In a large nonstick skillet, melt 1 tablespoon butter over medium-high heat. Cook the patties in a single layer on the first side until they are well browned, about 5 minutes (no need to flip them in the pan). Transfer to large plate, browned-side up. If needed, cook the patties in batches so they do not touch while browning.
To the pan with the patty drippings, add the onions and remaining ½ teaspoon salt. Cook, stirring occasionally, until the onions are turning golden brown, about 8 minutes.
Reduce the skillet heat to medium. With a spatula, carefully transfer the patties to the skillet and place them on top of the onions, keeping the browned-side up. Pour in any juices that have collected on the plate around the patties.
Let the patties cook, shaking the pan every few minutes to loosen up the onions, until onions are tender and the burgers are cooked through; they should register at least 135°F on an instant read thermometer, about 3 to 5 minutes. Note the burgers temperature will continue to rise and do not overcook or the patty melts will be dry. Remove the patties and onions to a plate.
Assemble the sandwiches: Place ¼ cup of shredded cheese on each of 3 slices of the bread. Top with patties, onions, remaining cheese, and the remaining 3 slices of bread.
With paper towels, carefully wipe the skillet fairly clean. Melt ½ tablespoon butter in the skillet over medium heat. Cook 2 sandwiches on both sides until golden brown and cheese is melted, about 3 minutes per side (if your skillet is very large, use all the butter and cook all 3 at once). Transfer to a baking sheet and keep warm in oven. Repeat with remaining ½ tablespoon butter and remaining sandwich. Slice and serve immediately.
Notes
TO STORE: Assembled patty melts do not keep well, so if you know you’ll have leftovers, store the patties and onions in the refrigerator, then assemble patty melts when you plan on eating them. The patties can be refrigerated for up to 3 days in an airtight container, while assembled patty melts will keep for 1-2 days.
TO REHEAT: To reheat the patties and onions, place them in a skillet over medium heat and cook each side of the patties until warmed through, then assemble your burgers and toast them as directed in the recipe. If your patty melts are already assembled, heat them in a 350ºF oven until warmed through. You can use the microwave in a pinch, but it’s harder to reheat a sandwich or burger evenly.