In a small bowl whisk together your egg and Worcestershire sauce, then thoroughly mix in the Garlic, Black Pepper, and Rosemary.
Place your meat into a large bowl. I like to poke holes all over the ground beef using my fingers to allow the liquids to get down into the meat. It makes for easier and more thorough mixing. Pour the egg mixture into the holes and over the meat.
Next dump in the 1 cup of chopped red onion and thoroughly mix. I don't add the cheese in at the same time as the liquids to avoid the cheese crumbles from falling apart.
Once the liquid mixture is thoroughly mixed into the meat, add 8 oz. of crumbled feta and 4 oz. of crumbled blue cheese. Again thoroughly mix this into the meat.
It's time to make the patties. There are no rules here. Make them round, square thin or thick. Form them the way you like them.
Cook these awesome burgers!