Sauté the onion in the butter in a small skillet until onion is tender. Cool completely.
Place the meat in a large bowl and gently toss in the onion-butter mixture, the mustard, garlic, Worcestershire sauce, pepper sauce, parsley and wine. Toss just until well mixed.
Using a very gentle touch, form into 8 patties.
Chill, covered, until ready to grill.
Grill on pre-heated hot grill to desired doneness. Turn only once
These rules apply to all burgers, whether plain or fancy: Form the patties with the lightest and gentlest touch possible. Never squeeze or press the ground beef. (Squeezing and pressing results in a dry, tough burger.) Always grill on a hot, preheated grill. Turn the burgers only once about 2/3 of the way through the cooking time. Never press with the spatula while cooking.