Beef Tenderloin Steak (or Filet Mignon) with Savory Koji Sauce
An effortless, restaurant-quality roast beef featuring tender beef tenderloin steak (or filet mignon) seared to perfection and cooked in a gentle rice cooker water bath. Marinated with a deeply savory, umami-rich shoyu koji and ama koji sauce, this dish delivers melt-in-your-mouth texture every single time.
Servings: 2 people
Calories: 520kcal
Equipment
- 1 Rice Cooker / Sous-Vide
Ingredients
The Beef & Tempering
- 2 pieces Beef Tenderloin Steak or Filet Mignon (approx. 0.6 lbs each, 1.2 to 1.4 lbs total)
- 8 g Sea Salt (accurately scaled to 1% of the total meat weight)
- 1-2 tbsp Avocado Oil (or any high-smoke-point oil for searing)
The Savory Koji Reduction Sauce
- 1/2 Medium Onion (finely minced)
- 2.5 tbsp Shoyu Koji (Soy Sauce Koji)
- 2.5 tbsp Ama Koji (Sweet Rice Koji / Amazake paste)
- 2 tbsp Hon Mirin
- 2 tsp Grated Garlic
- 1 tbsp Red Wine
- 1/2 tbsp Apple Cider Vinegar (or Balsamic Vinegar, reserved for reducing)
- 1 tbsp Unsalted Butter (optional, for finishing)
Instructions
Temper and Season the Meat
- Remove the beef from the refrigerator and place it on a clean tray. Evenly sprinkle the 8g of sea salt over all sides of the beef, gently rubbing it in. Let the meat sit at room temperature for 1 to 2 hours until it no longer feels cold to the touch.
High-Heat Golden Sear
- Heat a skillet over medium-high heat and add 1 to 2 tablespoons of avocado oil. Sear the beef for 60 to 90 seconds per side until a deep golden-brown crust forms. Sear the narrower sides for about 40 seconds.
- Remove the beef from the pan and let it cool slightly.
Prepare Sauce Marinade & Seal
- In a heavy-duty, heat-safe resealable bag (such as a Ziploc freezer bag), add the minced onion, shoyu koji, ama koji, hon mirin, grated garlic, and red wine. Mix well with a small flexible spatula directly inside the bag until evenly combined.
- Add the slightly cooled beef to the bag. Turn and massage the meat through the bag (or use your spatula) to ensure every part of the steak is evenly coated in the koji sauce.
- Carefully press out as much air as possible to create a tight vacuum seal, then seal tightly. (Double-bag if needed).
Gentle Rice Cooker "Sous-Vide"
- Fill your rice cooker inner pot with warm water heated to 140°F (60°C).Place a small heat-safe bowl or silicone mat upside down at the bottom of the pot to prevent the bag from resting directly on the heat source.
- Submerge the bagged beef completely. (If the bag floats, place a small heat-safe saucer on top as a weight).
- Close the lid, set to "Keep Warm", and hold for 45 minutes (extend to 1 hour if cuts are very thick).
- Remove the bag from the water bath. Take the beef out of the bag, place it on a plate, and tent loosely with aluminum foil for 5 to 10 minutes to retain its juices. Do not discard the marinade or juices in the bag.
Reduce the Koji Sauce
- Pour all the remaining liquid and minced onions from the bag into your skillet.
- Add 1/2 tablespoon of apple cider vinegar (or balsamic).Simmer over medium heat until the sauce reduces into a glossy, slightly thickened glaze.
- Optional: Whisk in 1 tablespoon of cold butter right at the end for extra richness. Taste and adjust with pepper if desired.
Slice and Serve
- Slice the beef into clean medallions against the grain.
- Arrange on a serving platter and spoon the warm shoyu koji reduction generously over the top.
Notes
- Meal Prep Friendly: This roast beef keeps exceptionally well in the refrigerator. Cook it in advance, keep it wrapped whole, and slice cold for bento boxes, grain bowls, or crisp salads!
- Equipment Note: If you own a dedicated Sous-Vide precision cooker or yogurt maker, set it to 140°F (60°C) for identical results.
Nutrition
Serving: 270g | Calories: 520kcal | Carbohydrates: 18g | Protein: 56g | Fat: 24g | Saturated Fat: 8.5g | Cholesterol: 145mg | Sodium: 1950mg | Sugar: 11g