Trim any large fat pieces from the steak and pat the meat dry with paper towels. Cut into roughly 1-inch cubes, keeping pieces as uniform as possible so they cook evenly.

Make marinade

In a medium bowl combine 2 tbs olive oil, 2 tbs soy sauce, 1 tbs Worcestershire sauce, minced garlic, 1 tsp freshly ground black pepper, and 1/2 tsp kosher salt. Whisk to combine.

Toss the steak cubes into the marinade and stir to coat thoroughly. Let marinate at room temperature for 15–20 minutes or refrigerate for up to 2 hours. If refrigerated, bring to room temperature for 20–30 minutes before cooking.

For Searing

Preheat pan

Place a large heavy skillet (cast iron preferred) over high heat and let it get very hot, about 3–5 minutes.

Sear in batches

Add 1 tbs neutral high-heat oil to the hot pan and swirl to coat. Remove steak from the marinade, letting excess drip off (reserve marinade). Add the steak cubes in a single layer without crowding — you may need to work in 2 batches. Sear undisturbed for 1.5–2 minutes to develop a brown crust, then flip and sear the other sides another 1–2 minutes for medium-rare to medium depending on cube size. Total cook time per batch ~3–4 minutes.

Finish with butter

In the last 30 seconds of searing, reduce heat to medium-high and add 1 tbs unsalted butter. Tilt the pan slightly and spoon the melted butter over the steak bites to baste and add flavor.

Transfer seared steak bites to a warm plate and tent loosely with foil while you cook remaining batches. If desired, after all batches are cooked, return all steak bites to the pan with any accumulated juices and heat 30 seconds to combine.

Finish & Garnish

Turn off heat. Sprinkle the steak bites with 2 tbs chopped fresh parsley, 1 tsp fresh lemon juice, and optional 1/4 tsp red pepper flakes. Toss gently to combine and taste; adjust salt and pepper if needed (add small pinch of salt if under-seasoned).

Serve immediately while hot as an appetizer with toothpicks or over rice, mashed potatoes, or salad as a main.