01 - Pat steak cubes dry with paper towels. Season evenly with salt and pepper.
02 - In a small bowl, mix sour cream, horseradish, Dijon mustard, lemon juice, salt, and pepper. Chill until ready to serve.
03 - Heat a large skillet over high heat. Add 1 tbsp butter and swirl to coat. Add half the steak cubes in a single layer. Sear for 1-2 minutes per side until browned but still medium-rare inside. Remove to a plate. Repeat with remaining steak cubes, adding another tablespoon of butter if needed.
04 - Reduce heat to medium. Add remaining butter and garlic to the skillet. Sauté 30 seconds until fragrant.
05 - Return all steak bites to the skillet, toss to coat with garlic butter, and sprinkle with chopped parsley. Serve immediately with horseradish cream and extra parsley if desired.