Step 1: Pat your steak cubes thoroughly dry with paper towels. Season generously on all sides with salt and freshly ground black pepper.
Step 2: Heat a large, heavy-bottomed skillet (preferably cast iron) over medium-high heat until slightly smoking (about 2-3 minutes). Add 1 tablespoon of olive oil and swirl to coat.
Step 3: Add about half of the steak cubes to the hot skillet in a single layer (do not overcrowd). Sear for 1-2 minutes per side until a deep, golden-brown crust forms. Remove to a plate and repeat with the remaining steak. Set all seared steak aside.
Step 4: Reduce heat to medium-low. Add 4 tablespoons of unsalted butter to the same skillet. Let it melt, scraping up any browned bits from the bottom. Add the minced garlic, dried thyme, and optional dried rosemary. Sauté for 30-60 seconds until fragrant, being careful not to burn the garlic.
Step 5: Return all the seared steak bites to the skillet with the fragrant garlic herb butter. Add the chopped fresh parsley and an optional pinch of red pepper flakes. Toss everything together for about 1 minute, ensuring all steak bites are evenly coated. Immediately remove from heat.
Step 6: Transfer your garlic herb butter steak bites to a serving platter and serve hot. Garnish with extra fresh parsley if desired. Enjoy immediately!