Preheat your oven to 350°F (175°C) and line a 9x13 inch baking sheet with foil or parchment paper.

Dice the onion finely and mince the jalapeños after removing the seeds. Shred the sharp cheddar cheese and soften the cream cheese.

In a large mixing bowl, combine ground beef, diced onion, eggs, Panko breadcrumbs, milk, salt, pepper, dried basil, and garlic powder, mixing gently.

Divide the meat mixture in half and shape the first half into a rectangle on the baking sheet, creating a slight indent down the center.

In a separate bowl, mix softened cream cheese, minced jalapeños, and shredded cheddar cheese, then spoon into the meat rectangle.

Cover the filling with the other half of the meat mixture, sealing the edges tightly.

Spread ketchup over the top and lay strips of bacon if using.

Bake in the preheated oven for 60 to 70 minutes, until internal temperature reaches 160°F (70°C).

Let it rest for 10 to 15 minutes before slicing into portions and serving.