Step 1

To quick dry-age steak, sprinkle koji rice powder over steaks to completely cover. Place steaks on a wire rack set over a tray uncovered in the refrigerator to dry age (48 hours)

Step 2

For miso butter, combine ingredients in a small food processor and process until smooth; season with pepper, then roll butter tightly in baking paper or plastic wrap to form a cylinder, twist the ends to seal and chill until needed.

Step 3

Rinse off koji powder and pat dry with paper towel. Bring steak to room temperature (30 minutes). Drizzle steak with 1 tbsp oil and lightly season. Heat 1 tbsp oil in a large frying pan over high heat. Cook steak to your liking (5-6 minutes for medium rare). Transfer to a board, cover loosely with foil and allow to rest (15 minutes; see note).

Step 4

Heat remaining 60ml (¼ cup) oil in the frying pan over high heat. Cook mushrooms, in batches, stirring occasionally, until golden (10 minutes). Transfer to a tray. Reduce temperature to low. Add half the miso butter to pan, swirling the pan, until nut brown (1-2 minutes). Add onion, leek, garlic and cook, stirring occasionally, until softened (3 minutes). Deglaze with whisky and simmer until reduced by half (2 minutes). Add stock, beans and Worcestershire. Return mushrooms. Bring to a simmer; simmer until sauce begins to thicken slightly (6-8 minutes). Remove from the heat. Stir in parsley and lemon juice; season to taste.

Step 5

Slice steak. Arrange bean and mushroom mixture on a serving plate. Top with steak and miso butter to serve.