Pull the Fullblood Wagyu ground beef patties from the freezer, and place them in the refrigerator 24 hours before starting this recipe.
PREPARING THE ONIONS
Heat a medium size sauté pan on medium heat. Then, add in the grapeseed oil and butter.
Once the butter has melted, add in the julienned sweet onions. Sprinkle the onions with kosher salt.
Cook the onions, while stirring occasionally, until they start to caramelize.
Once the onions and the bottom of the pan have some caramelization, add in the 1/4 cup of water and the Worcestershire sauce.
Using a wooden spoon, scrape the bottom of the pan to pull up the brown bits and caramelization.
The onions will take about 20 minutes to caramelize, so don’t rush this process.
Once the onions are caramelized, set them aside.
PREPARING THE INSIDE SPREAD
In a small bowl, mix together the mayonnaise, ketchup, and dijon mustard. This is your inside spread.
Set aside for later use.
PREPARING THE FULLBLOOD WAGYU GROUND BEEF PATTIES
Heat a large saute pan to medium-high heat.
Sprinkle the Fullblood Wagyu ground beef patties with kosher salt and freshly ground black pepper.
Once the pan is heated, add in one tablespoon of grapeseed oil.
Sear off the beef patties for 2-3 minutes per side (cook for 2 minutes per side for a medium-rare finish).
Once the patties are seared on both sides, place them on a plate to rest.
PREPARING THE PATTY MELTS
Place the 8 slices of rye bread down on a cutting board, and smear all of the pieces with the inside spread.
On 4 pieces of bread, place a piece of each of the three cheeses (swiss, provolone, and sharp cheddar).
On the other 4 pieces of bread, place the seared Fullblood Wagyu beef patty. Top the patty with the caramelized onions.
Place the two sides of bread together to form the patty melt.
Heat a large square skillet pan on medium-high heat.
Spread mayonnaise on the side of the bread going down into the pan first.
Once the Patty melt is down in the pan, spread the side of bread facing up with mayonnaise.
Toast the patty melt for about 2 minutes per side.
When finished, the patty melts should be a nice golden brown, and the cheese should be melted.
Place the cooked patty melts on a cutting board, and let them cool for a few minutes.
Using a serrated knife, carefully cut the Fullblood Wagyu ground beef patty melt in half.
Serve hot, and enjoy!