Vegan Udon Noodle Soup with Spring Vegetables

Name: Vegan Udon Noodle Soup with Spring Vegetables
Ingredients: 3 bundles of dried flat udon noodles; 40 snow peas, halved; 12 broccolini; 20 asparagus spears, tough ends snapped off (mine were thin, if you’ve got thick ones you may need less than 20); A small bunch of enoki mushrooms (100 grams / 3.5 oz); 4 radishes, thinly sliced; 1 green onion, thinly sliced; The zest of one lemon; Sesame seeds to garnish (optional); 4 cups (1 litre) water; A 5 gram (0.2 oz) piece of kombu (about 10 cm² / 4 in²); 2 dried shiitake mushrooms; 2 tablespoons mirin; 2 tablespoons soy sauce; 1 tablespoon sake; 1 teaspoon sea salt (or to taste)