In a large bowl, whisk together vinegar, mustard, honey, 2 Tbsp oil,1/2 tsp salt, and 1/4 tsp pepper; stir in shallot and horseradish.  Heat remaining 2 tsp oil in a large skillet on medium-high. Season steak with 1/2 tsp each salt and pepper and cook to desired doneness, 3 to5 minutes per side for medium-rare. Transfer to a cutting board and let rest for at least 5 minutes before slicing. While steak is resting, toss cucumbers and apple with shallot mixture. Fold in cress and serve with steak.