In a large measuring cup, whisk 2.5 cups beef stock with Worcestershire, bouillon, garlic powder, mustard powder, sage, thyme, black pepper, and Kitchen Bouquet (if using). Set aside.

Pat steak dry, lightly tenderize with a meat mallet, then rub with 1–2 tbsp avocado oil and the steak seasoning.

Heat a Dutch oven or large skillet over medium-high. Add 2 tbsp avocado oil and sear steak 2–3 minutes per side until well browned; work in batches to avoid crowding. Transfer steak to a plate.

Reduce heat to low. Add 1/2 cup beef stock and 1 tbsp apple cider vinegar to deglaze, scraping up browned bits.

Add butter. When melted, stir in onions with a pinch of salt; cook 6–8 minutes until softened and lightly caramelized. Add garlic and cook 30–45 seconds until fragrant.

Sprinkle flour over the onions and stir constantly for 1 minute to form a roux.

Slowly whisk in the prepared stock mixture. Bring to a gentle simmer, whisking until smooth and slightly thickened.

Return steak (and any juices) to the pot, submerging in the gravy. Cover and simmer on low for 2.5–3 hours (or until fork-tender). Keep the simmer gentle; add splashes of stock if needed.

Taste and adjust seasoning with salt and pepper. For a richer finish, simmer uncovered briefly to reduce to desired thickness.

Serve steak and gravy generously over cooked white rice. Garnish with chopped parsley or chives if desired.