Mix hamburger, worcestershire, water and 1/4 of the onion, some seasoning to taste and mold into big patties. I then dig out the middles to add ingredients into. (You want a fairly deep well for ingredients) I put everything directly in the hamburgers.
Add onion, jalapeno cheese(or white american if you don't want the spice)I dab on a little more of the worcestershire sauce, add little cubes of cream cheese, and season. You'll have to play around with the amounts of these ingredients until you get the desired amount for you. Just be sure to not put too much or it'll be too hard to grill without leaking!! With the cream cheese a little goes along way. The cubes are the size of peas or so.
Cover up center of patty and refrigerate for 1/2 hr. before grilling so that the meat stays together. Grill till desired doneness. When you bite into one of these the cream cheese and cheese melts all over!! Everyone that's tried these loved the surprise filling!!! Just be sure to tell them that they probably don't need to add much on top of the burgers( I just put a thin slice of the jalapeno cheese and an onion slice and a little salt and pepper.) You can vary with the seasoning or cheese or add bell pepper or bits of tomato or whatever suits you!! It's very versatile!! It's the cream cheese and cheese INSIDE the hamburger that makes the melty difference!!! Enjoy!!