Cut the beef into 1-inch cubes, and put into a freezer bag with the olive oil, 1 tablespoon grated fresh horseradish or horseradish sauce, rosemary, vinegar, Worcestershire sauce, and port. Set aside for at least 20 minutes, but preferably overnight, in the fridge.

Let the meat come to room temperature, and soak about 10 bamboo skewers in water at the same time.

Make the dip by beating together the crème fraîche or sour cream and the remaining 2 tablespoons of freshly grated horseradish or hot horseradish sauce with the mustard and salt. Stir in the chives, leaving some chives to sprinkle over the top.

Heat a grill or griddle, then thread three or four pieces of meat onto each skewer and slap on the heat, turning after 2 minutes. Cook for another 2 minutes on the other side and then remove to a plate, strewn with some sprigs of rosemary if desired. Do not serve while grill-hot.