Preheat the oven to 350°F. Lightly spray a 9x13-inch baking dish with nonstick cooking spray.
In a large skillet over medium heat, add oil. Once hot and shimmering, add the diced onion and cook until softened, about 3 to 4 minutes.
Stir in the garlic and cook for about 30 seconds.
Add the ground beef to the skillet. Break it apart with a wooden spoon and cook until no pink remains, 8 to 10 minutes. Drain excess grease.
Stir in the Worcestershire sauce, hamburger seasoning, seasoned salt, kosher salt, and pepper. Remove from heat and set aside.
In a small bowl, stir together the melted butter, garlic, parsley, and salt. Set aside.
Without separating the rolls, slice them horizontally through the middle. Place the bottom half into the prepared baking dish.
Lay 6 slices of cheddar cheese evenly over the bottom buns.
Spread the cooked beef mixture evenly over the cheese layer, gently pressing it into an even layer.
Lay the remaining 6 slices of cheddar cheese over the beef.
Spoon the prepared bacon jam evenly over the top cheese layer, spreading it gently so it reaches the edges.
Place the top half of the rolls over the bacon jam layer.
Brush the tops of the rolls generously with the garlic butter mixture. Sprinkle with sesame seeds, if using.
Cover loosely with aluminum foil and bake for 15 minutes, or until the cheese is melted and heated through.
Remove the foil and bake an additional 5 minutes, or until the tops are golden brown.
Remove from the oven, let rest for 5 minutes, then slice and serve warm.