I mix ground round and ground chuck. I prefer thinner patties, so get about 5 patties per pound of beef. I also like plain beef, nothing added. I flatten the patties a little larger than the bun. They can be grilled, broiled, or fryed at this point. (Cook well done, however) I warm the buns in the oven wrapped in foil. To assemble, spread the bun with mayonnaise and a touch of mustard ( I like yellow mustard); a slice of onion and dill pickle on top half of bun; lettuce and tomato on bottom half of the bun; salt and pepper to taste; place the pattie on the bun and enjoy all the fat grams and calories. What goes on the meat and on the bun is up to individual tastes.