Baconnaise Patty Melts with Caramelized Onions

Place a large skillet or griddle over medium heat.

Lay out all eight slices of thick-cut bacon in a single layer, working in batches if necessary to avoid crowding.

Cook for three to four minutes per side, flipping occasionally, until the bacon is deeply browned and crispy.

The bacon should shatter rather than bend when you try to break it – this level of crispness is crucial for both the baconnaise and the sandwich topping.

Transfer the cooked bacon to a paper towel-lined plate to drain.

Once cool enough to handle, set aside four whole slices for topping the sandwiches.

Finely chop the remaining four slices for the baconnaise – the pieces should be almost minced, barely larger than coarse breadcrumbs.

Reserve one tablespoon of the bacon grease in a small bowl for cooking the onions – don’t discard it down the drain as it adds crucial flavor.

In a small bowl, combine the half cup of mayonnaise with the finely chopped bacon, one teaspoon of Dijon mustard, half teaspoon of smoked paprika, half teaspoon of garlic powder, pinch of cayenne if using, and one teaspoon of fresh lemon juice.

Stir everything together vigorously with a spoon until the bacon pieces are evenly distributed throughout the mayo and no white streaks remain.

The baconnaise should be pale tan with visible bacon pieces throughout and smell intensely of smoky bacon.

Taste carefully – it should be creamy with prominent bacon flavor, slight tang from the mustard and lemon, and warming spice notes from the paprika and garlic.

Adjust seasoning if needed, though remember it will taste strong now because you’re tasting it straight rather than in the context of the sandwich.

Cover and refrigerate while you prepare the other components.

The cold helps it firm up and allows the flavors to meld.

Using a mandolin, slice the large yellow onion into paper-thin rounds, about one-sixteenth inch thick.

Use the hand guard for safety – mandolins are extremely sharp.

Separate the onion slices into individual rings.

You should have about two to three cups of sliced onions.

In a large skillet, melt the two tablespoons of butter over medium-low heat.

Add the reserved tablespoon of bacon grease to the melted butter – the bacon fat adds smoky depth that ties the onions into the overall flavor profile.

Add all the sliced onions to the pan and toss to coat them evenly in the fat.

Season lightly with a pinch of kosher salt.

Cook the onions over medium-low heat for fifteen to twenty minutes, stirring every three to four minutes to ensure even cooking.

At first, the onions will release moisture and seem wet and steamy.

Don’t increase the heat to speed things up – this will burn them.

Continue cooking patiently.

After about ten minutes, once most of the moisture has evaporated, the onions will start to brown and shrink significantly.

Add the two teaspoons of Worcestershire sauce and stir to distribute evenly.

Continue cooking, stirring more frequently now, until the onions are deeply golden-brown, soft, and jammy.

They should be sweet with caramelized edges and almost spreadable consistency.

The finished onions will have reduced to about one cup in volume.

Remove from heat and set aside.

The onions can be made ahead and refrigerated for up to three days.

Divide the one and a half pounds of ground chuck into four equal portions of about six ounces each.

Working with one portion at a time, gently form the meat into a thin patty about half-inch thick and slightly larger than your bread slices – they’ll shrink during cooking.

Don’t overwork the meat or compress it too tightly, which creates dense, tough patties.

The patties should just barely hold together.

Season both sides of each patty generously with kosher salt and cracked black pepper.

Use more seasoning than seems reasonable – the beef can handle aggressive seasoning and much will fall off during cooking.

Let the seasoned patties sit at room temperature while you heat the cooking surface.

Heat a large griddle or cast iron skillet over medium-high heat for three to four minutes until very hot.

Add the patties to the hot surface – you should hear immediate, aggressive sizzling.

Don’t move them once they’re down.

Cook for two to three minutes on the first side until deeply browned with a crust developing around the edges.

Flip the patties and cook another two to three minutes on the second side until browned and cooked through to about 160°F internal temperature.

The patties should be well-done since they’re thin and will be reheated during the final griddling of the assembled sandwiches.

Transfer the cooked patties to a plate and let rest for a minute or two.

The brief rest allows juices to redistribute, though with thin patties this is less critical than with thick burgers.

Lay out all eight slices of Texas toast.

Spread softened butter on one side of each slice – this buttered side will be the exterior that gets griddled.

Be generous with the butter as it creates the golden-brown crust and rich flavor.

On the unbuttered side of four slices, spread a generous layer of the baconnaise – about two tablespoons per slice.

Don’t skimp – the baconnaise is a key flavor component.

Place one slice of Swiss or American cheese on top of the baconnaise on each of the four slices.

Add a cooked beef patty on top of the cheese.

Season the patty with a tiny pinch more salt if desired.

Spread a quarter of the caramelized onions over each patty – the onions should cover the entire surface of the meat.

Place a whole crispy bacon strip on top of the onions, breaking it to fit if necessary.

Add another slice of cheese on top of the bacon – this cheese will melt down over everything, binding the layers together.

Top with the remaining four bread slices, buttered side facing out.

Press down gently on each sandwich to compact the layers slightly.

The sandwiches are now ready to griddle.

Heat a large griddle or two large skillets over medium heat.

Medium heat is crucial – too hot and the bread burns before the cheese melts; too cool and the bread doesn’t crisp properly.

Place the assembled sandwiches on the hot surface, working in batches if necessary to avoid crowding.

Place a heavy skillet or burger press on top of each sandwich to press it flat.

This ensures good contact between the buttered bread and the hot surface while helping the cheese melt.

Cook for three to four minutes without moving until the bottom is deeply golden brown.

Carefully peek under one corner to check – when it’s beautiful golden-brown, it’s ready to flip.

Flip the sandwiches carefully using a large spatula, supporting the sandwich with your other hand if needed to prevent it from falling apart.

Press again with the weight and cook another three to four minutes until the second side is golden brown and the cheese is completely melted.

The cheese should be visibly oozing from the sides.

Remove from heat and let the patty melts rest for one to two minutes before cutting.

This brief rest allows the cheese to set slightly so it doesn’t all run out when you cut into the sandwich.

The rest also makes them easier to handle and less likely to burn your mouth.

Using a sharp knife, cut each patty melt in half diagonally.

The diagonal cut exposes the cross-section beautifully – you should see distinct layers of golden bread, melted cheese, beef patty, caramelized onions, and bacon.

The interior should be steaming with the cheese gooey and stretchy.

Serve the patty melts immediately while hot.

The bread should be crispy and golden on the outside, the cheese should be molten, and the beef should be juicy.

Each bite should deliver crunchy bread, creamy baconnaise and melted cheese, savory beef, sweet onions, and smoky bacon.

The flavors should be balanced – rich but not greasy, savory with sweet notes from the onions, and smoky bacon presence throughout.