Start by placing your sirloin steak on a clean cutting board. Trim away excess fat and cut into 1-inch cubes.

In a medium mixing bowl, combine balsamic vinegar, olive oil, minced garlic, Dijon mustard, dried oregano, black pepper, and sea salt. Whisk until well blended.

Add cubed steak to the marinade and gently toss until thoroughly coated. Cover and refrigerate for at least 30 minutes.

Heat a large nonstick skillet over medium-high heat until hot.

Add the marinated steak cubes to the skillet in a single layer and cook for about 2 to 3 minutes per side.

After cooking, remove from heat and let them rest for 5 minutes.

Sprinkle chopped fresh parsley over the steak bites before serving.