Preheat a grill pan to medium-high heat, or even better, preheat a charcoal grill if you can grill outside.
In a bowl put the ground beef, onion, garlic, Worcestershire sauce, parsley, salt and pepper and combine with a fork.
With your hands form the patties and place them on the preheated pan or grill, and cook them for 4 minutes.
Flip the patties and cook them for 4 more minutes, depending on your desired wellness.
One minute before the patties are done, place the cheese on top. Once done, let the patties rest for 3-5 minutes.
Open buns and spread half of them with mustard and the other half with mayo.
Put lettuce in the bottom part of the slider bun.
Place the patties over the lettuce and continue with tomato and onion.
Add some ketchup and cover with the other side of the bun.
Secure with a bamboo skewer and enjoy your big win.