In a pan over high heat, add olive oil and thinly sliced rib eye. Season with salt, black pepper and garlic powder.
Cook until half way done and add in the minced onion, green pepper and season with a pinch of salt and pepper.
Continue cooking until the steak is to your preferred doneness and the onions and green pepper are tender and slightly browned. Set aside and allow to cool.
Roll out the puff pastry and cut into 3 inch wide strips. You should be able to get 4-5 strips from one roll.
First lay down some American cheese, followed by the cooked steak, then a half slice of American and a half slice of mozzarella cheese. Make sure to leave room around the edges.
Fold over the empty side and using a fork, crimp the edges to seal completely.
Transfer to a parchment lined baking sheet and make 3 cuts across the tops to allow air to pass through.
Brush on melted butter and top with parmesan cheese and place in a preheated oven at 425F.
Bake for 14-16 minutes until cooked through and golden brown.