Beef Steak Donburi

Ingredients for Beef Steak Donburi (serves 2) 2 cuts of 100g Steak - beef tenderloin or sirloin (3½ oz) Salt Pepper 80g Onion (2.8 oz) 50g Eringi Mushroom - King Oyster Mushroom (1¾ oz) 2 Lettuce Leaves - Onion Ponzu Sauce - 2 tbsp Sake 3 tbsp Grated Onion 3 tbsp Ponzu - citrus-based sauce ½ tbsp Grated Garlic ½ tbsp Butter - Quick Homemade Ponzu - 1½ tbsp Soy Sauce 1½ tbsp Any type of Sour Citrus Juice (ex. yuzu, lemon or lime) 1 tsp Mirin or substitute: a sprinkle of sugar A sprinkle of Dashi Powder 3