01 - Combine sour cream, horseradish, Dijon mustard, lemon juice, salt, and pepper in a small bowl. Mix thoroughly and refrigerate until serving.
02 - Season steak cubes generously with salt and pepper on all sides.
03 - Heat olive oil in a large skillet over high heat until shimmering.
04 - Add steak cubes in a single layer, working in batches if needed. Sear for 2 minutes per side until browned and just cooked through. Remove to a plate and cover loosely with foil.
05 - Reduce heat to medium. Add butter to the pan and melt completely. Stir in minced garlic and cook for 30 seconds until fragrant.
06 - Return steak bites to the skillet and toss to coat in garlic butter. Cook for 1 minute. Stir in chopped parsley.
07 - Transfer steak bites to a serving platter. Serve with horseradish cream in a small bowl for dipping. Garnish with additional fresh parsley if desired.