Sakana No Nitsuke (Japanese Simmered Fish)

Ingredients

• 2 fillets of fish
• 2 Pinches salt
• 20g fresh ginger
• 1 bowl of freshly boiled water
• 1 bowl of ice cold water
• 150ml water
• 150ml sake
• 45 ml mirin (3 tbsp)
• 30g sugar (2 1/2 tbsp)
• 50ml soy sauce
• 1/3 bunch of "Komatsuna" Japanese mustard spinach (You could also use regular spinach or bok choi instead)