In a bowl, combine a drizzle of oil, Sriracha, pepper, and soy sauce to create a marinade. Add the beef steak strips and coat them well. Cover and let it marinate for at least 30 minutes at room temperature.

Heat a large skillet over medium-high heat and add a tablespoon of butter. Sear the marinated steak strips lightly with salt and pepper, for 1-2 minutes on each side until golden-brown. Transfer the steak to a covered plate to rest.

Reduce the heat to medium, add more butter if needed, and sauté shallots and garlic for about 2 minutes until softened and fragrant.

Add thyme, chives, and chili pepper flakes, then pour in lemon juice, mustard, and beef stock, scraping any brown bits. Let simmer for about 5 minutes until reduced by half.

Stir in 2 tablespoons of butter into the sauce until melted completely. Taste and adjust seasoning with salt and pepper.

Return the rested steak to the skillet, reheating briefly in the sauce for about a minute. Serve with the butter sauce drizzled on top.