Cook the ramen noodles according to packet directions. Drain and sit aside if you want them warm, or run under cold water if you prefer cold noodles.
250 g ramen noodles
Heat the vegetable oil in a small saucepan over a low-medium heat. Add the spring onion, ginger and garlic and fry for 1-2 mins until fragrant.
½ tbsp vegetable oil, ½ cup spring onion, 1 tsp ginger, 1 tsp garlic
Add the soy sauce, mirin, sugar, rice wine vinegar and chicken stock then increase the heat to medium-high and bring to the boil. Add the katsuobushi / bonito flakes and stir again.
1 tbsp soy sauce, ½ tbsp mirin, 1 tsp sugar, 1 tsp rice wine vinegar, 200 ml chicken stock, 2 tbsp bonito flakes / katsuobushi
In a small dish, mix together the cold water and cornstarch / cornflour to form a slurry. Pour into the soup and stir to thicken (around 1-2 minutes). Turn off the heat.
1 tbsp cold water, 2 tsp cornstarch / cornflour
Place the red miso into a strainer and dunk into the soup. Use a spoon to dissolve the miso paste.
2 tbsp red miso paste
Optional: Add the rayu chilli oil and stir through.
1/4 tsp rayu chilli oil
Portion out the tsukemen soup into two small bowls. Place the ramen noodles into separate bowls ready to dip.