Brush the flank steak with 2 tablespoons soy sauce. Sprinkle well with pepper and thyme, let marinate for 1 hour.
Brush again with the remaining 2 tablespoons soy sauce and grill or broil over high heat 4-5 minutes per side for rare. Let rest 10 minutes and then carve with a sharp knife in thin slices on the diagonal.
Combine the shallots and red wine in a sauce pan bring just to the boiling point.
Add the butter in chunks stir.Stir until the butter is melted. Add parsley.
Taste and add salt if desired. Spoon over steak slices.