Boiled Squid with Miso Vinaigrette

Bahan-bahan (2 porsi)

• 2 spear squid ((fresh; yari ika in Japanese))
• 3 g reen onions/scallions
• Diamond Crystal kosher salt
• 2 Tbsp miso ((I used white miso))
• 2 Tbsp rice vinegar (unseasoned)
• 2 Tbsp sugar
• ½ tsp mirin
• Japanese karashi hot mustard ((optional))