Soak dried onions in hot water for 5 to 10 minutes. Drain.
Season steaks with salt and pepper and refrigerate for 1 hour.
Melt 3 tablespoons butter in a frying pan. Add the mustard and 2 tablespoons of the onions. Sauté for 1 minute over medium-high heat.
Add steaks and brown for about 3 to 4 minutes each side (until medium-rare). Remove steaks to a platter and keep warm.
Add remaining butter, lemon juice, Worcestershire sauce, garlic, remaining onion and the water gravy mixture to the pan drippings. Cook for about 2 minutes, then add mushrooms and brandy or wine.
Boil, stirring frequently, until gravy is reduced to about 1/2 cup. Pour over steaks, sprinkle with parsley, and serve.