Siomai Babi (Pangsit Babi Kukus)

Bahan-bahan (35 porsi)

• ¾ onion ((7 oz, 200 g))
• 2½ Tbsp potato starch or cornstarch
• 14 oz ground pork ((⅞ lb))
• 1 tsp ginger ((grated, with juice; from a 1-inch, 2.5-cm knob))
• 1 Tbsp sake
• ½ Tbsp toasted sesame oil
• 2 tsp sugar
• 1 Tbsp soy sauce
• ½ tsp Diamond Crystal kosher salt
• ⅛ tsp white pepper powder
• 35 wonton wrappers
• 3 Tbsp green peas ((1 oz))
• soy sauce
• rice vinegar (unseasoned)
• la-yu (Japanese chili oil)
• Japanese karashi hot mustard ((optional))