Preheat your oven to 400°F. Slice the bread lengthwise and arrange it on a baking sheet lined with parchment paper.

Combine softened butter, garlic powder, and salt. Spread the mixture evenly over the cut sides of the bread. Bake for about 10 minutes until golden and crisp. Remove from the oven and set aside. Lower the oven temperature to 350°F.

In a skillet over medium heat, cook the ground beef and diced onion until the beef is browned and the onion is tender. Drain any excess fat.

Stir in water, ketchup, mustard, garlic powder, Worcestershire sauce, salt, and pepper into the beef mixture. Let it simmer for 5 minutes.

Combine the grated Cheddar and Pepper Jack cheeses in a bowl and mix well.

Spread the beef mixture over the toasted bread halves. Sprinkle the cheese blend evenly on top.

Bake in the oven at 350°F for 10-12 minutes, or until the cheese is thoroughly melted. If desired, broil for an additional minute to achieve a golden-brown top.

Once done, take out from the oven and let it cool for a few minutes. Garnish with parsley if using, slice, and serve.

Enjoy!