1) Carefully mix the meats, bread crumbs, steak sauce, eggs, salt, and pepper with the tines of a fork, but do not mash them. Lightly form hamburger patties and press lightly into shape.
2) Prepare a charcoal barbecue or stove-top griddle.
3) Cook the hamburgers for 4 mins on 1 side, then turn and cook 3 mins on the other side for medium-rare. Remove to a plate and cover with aluminium foil. Allow the hamburgers to rest for 5 mins.
4) Meanwhile, griddle the baps, cut side down, for 1 min, until toasted. Place a hamburger and a slice of blue cheese in each bap, plus rocket and tomato, if desired, and serve hot.