Make the crotes: In a large frying pan, heat the butter and olive oil until it stops sizzling and fry the sliced bread on each side, over medium heat, until golden. Remove to a plate and wipe the pan clean.
Season the steaks liberally with salt and pepper. Heat half the remaining butter and olive oil in the frying pan over high heat until it stops sizzling, then add two of the steaks. Cook about 2 minutes on each side, or longer for well-done meat.
Remove and keep warm. Add the rest of the butter and olive oil and repeat for the other two steaks.
Add the chopped shallots to the frying pan and cook one minute. Pour in the wine and cook over very high heat until reduced to nearly a glaze, 3 minutes. Pour in the stock and reduce again to about 3/4 cup. Off the heat, stir in the butter, Worcestershire sauce, capers, mustard and parsley. Taste for seasoning.
Place a crote on each of four plates. Lay a steak on each crote, then spoon over the sauce. Serve immediately.