Salmon noodle soup with wild mushrooms and greens

Ingredients

• 1 1/2 litres quality fish stock
• 1 spring onion, roughly chopped
• 2 slices or 3 slices fresh ginger
• 5 centimetre stick lemongrass or ½ teaspoon, finely chopped
• 2 packets soba noodles (approx. 180g each)
• 350 grams fresh salmon fillets, skinless, boneless, cut into bite-sized slices
• 2 small bok choy, chopped
• 2 cups chinese cabbage, finely shredded
• 100 grams wild mushrooms or mixed mushrooms, finely sliced
• 1/4 cup sweet soy sauce (kecap manis)
• 2 teaspoons toasted sesame seeds or mixed white and black sesame seeds