Marinate the Steak:
In a bowl, whisk together the soy sauce, olive oil, hot sauce, and black pepper. Add the steak strips and toss to coat. Marinate for at least 30 minutes in the refrigerator.

Sear the Steak:
Heat 1 tablespoon of butter in a skillet over medium-high heat. Remove the steak from the marinade, pat dry slightly, and season with a bit of salt and pepper. Sear the strips for 1–2 minutes per side until browned. Transfer to a plate and cover to keep warm.

Make the Sauce:
Lower the heat to medium. In the same skillet, add the chopped shallot and minced garlic. Sauté for about 2 minutes until fragrant and soft. Stir in thyme, chives, red pepper flakes, lemon juice, mustard, and beef stock. Scrape up any browned bits from the pan. Simmer for about 5 minutes until the liquid is reduced by half.

Finish the Sauce:
Add the remaining 2 tablespoons of butter to the pan, swirling to melt. Taste and adjust the seasoning with salt and pepper.

Combine & Serve:
Return the steak strips to the skillet and heat briefly in the sauce. Garnish with chopped parsley and serve warm with your choice of roasted vegetables or sautéed greens.