Mix the water, soy sauce, pear juice, sesame oil, sugar, garlic, ginger and black pepper in a large mixing bowl. Add in the thinly sliced beef, shiitake mushrooms, carrots, leek, onions and spring onions and stir through to coat evenly in the marinade.
300 g tenderloin steak, 4 shiitake mushrooms, 2 carrots, 1 leek, 2 onion, ½ cup water, 4 tbsp soy sauce, 4 tbsp pear juice, 2 tbsp sesame oil, 2 tsp sugar, 2 tsp garlic, 2 tsp ginger, 1 tsp black pepper, 2 spring onion / green onion