In a medium saucepan, combine 1.4 litres of chicken stock, 2 garlic cloves (crushed) and a 2.5 cm piece of fresh ginger (thinly sliced). Bring to a gentle simmer over medium heat and cook for 10 minutes.
Meanwhile, bring a separate pan of water to the boil. Gently add 2 large eggs and cook for 6–7 minutes for a soft-boiled yolk. Transfer the eggs to an ice bath to cool, then peel and set aside.
Strain the stock through a sieve to remove the garlic and ginger.
Stir in 60 ml soy sauce and 30 ml mirin (or, as an alternative, 1 tsp caster sugar and 1 tbsp rice vinegar).
Add 115 g chestnut mushrooms (sliced) and simmer for 3–5 minutes until tender.
Stir in 60 g baby spinach leaves and cook for 1 minute until wilted. Taste and add more soy sauce if needed.
Meanwhile, cook 4 packets of dried ramen noodles in a separate pan of boiling water for 3–4 minutes until just tender. Drain well.
Divide the noodles between two bowls and ladle over the hot stock with mushrooms and spinach.
Cut each soft-boiled egg in half and place two halves on top of each bowl.
Garnish with sliced spring onions and a drizzle of sesame oil just before serving.