Slice hoagie rolls open.

Heat a large skillet over medium high heat and add 1 Tablespoon butter. Once the butter is melted, place the hoagies on the skillet so that the inside surface gets toasted (it will take 2-3 minutes). Set toasted buns aside.

Add remaining butter to pan and saute onions until they are translucent (about 3 minutes). Push onions to the side of the pan and add ground beef to the pan as one large patty. Let the ground beef start to brown without breaking it up (let it sear for 3-4 minutes).

Season with salt, pepper, and garlic powder and then flip the large ground beef patty over to sear the other side (it should take 2-3 minutes).

Start to chop up the ground beef using a spatula or ChopStir and work the onions in with the beef. Continue to chop and cook the beef until no pink remains (should take about 3 minutes).

Divide the meat into 4 even portions and top each portion with 2 slices of cheese. Allow the cheese to melt while in the skillet.

Spread mayonnaise and ketchup on the inside of the buns, then top with beef and cheese mixture. Add other preferred toppings (like tomatoes and lettuce) and then serve.