Tahini ramen

Name: Tahini ramen
Cuisine: Asian, Japanese
Ingredients: 500ml (174 oz/scant 2 cups) vegetable stock; 3 large dried shitake mushrooms; 1 x 5mm (/in) piece of fresh root ginger, skin on; 1 x 5-7cm (2-3in) piece of kombu seaweed (optional); 250ml (8½f oz/generous 1 cup) soya milk; 1 tbsp tamari (or soy sauce), or to taste; 70g (30z/⅓ cup) tahini; 1½ tsp sesame oil; vegetable oil, for frying; ½ leek, sliced about 5mm (/in) thick; 100g (3½2oz) mixed mushrooms (I like oyster and chestnut/cremini), torn into even bite-sized pieces; black pepper; 200g (7oz) ready-to-eat udon noodles; 2 soft-boiled eggs, halved (optional); 1 tbsp peanut rayu; 2 spring onions (scallions), cut into strips