Slice your steak across the grain (cut across the short side and down the whole length) Slice the steak into thin slices. I then sprinkle all the slices with a little Worcestershire sauce. *You can make the steak a day ahead of time and slice it the day you serve this appetizer. The steak can be served cold on the warm bread or you can reheat the steak in a hot skillet for a few minutes and then be sure to let it rest again before slicing.
If you choose to make the horseradish cream, combine your sour cream, horseradish to taste, salt, pepper, and garlic powder, parsley and stir until smooth.
Lay your steak slices across each slice of bread (2 slices of steak on each bread) top with the horseradish cream and another sprinkle of black pepper.
You can also garnish with sliced chives or green onions.