2) When both pieces are done, return them to the bag and leave to marinate for 24 to 48 hours in the refrigerator. Remove the meat from the refrigerator at least 20 minutes prior to grilling.
3) In a medium-sized bowl, combine the sour cream, mayonnaise, lemon juice, horseradish, garlic and sea salt and pepper, to taste. Mix thoroughly and place into the refrigerator for at least 4 hours.
4) Set a griddle or large grilling pan to a high heat. Cook the meat for 20 minutes or until desired temperature – it's best served medium-rare. Remove from the heat, cover and leave to rest for 5 to 10 minutes.
5) Slice the cooked and rested steaks paper thin using either a knife or counter-top deli-slicer. Place 125g of meat on a slice of toasted rye and spread on the sour cream horseradish.