Line a large baking sheet with parchment paper; set aside.

Place pork sausage, sake, rice flour, 1 Tbsp. coconut aminos, gingerroot and white pepper in a large bowl; mix until well combined.

Add bread crumbs, water chestnuts, ¼ cup green onions and egg; mix until a thick paste forms. With wet hands, shape sausage mixture into 12 meatballs, using almost ¼ cup for each. Place on prepared baking sheet; refrigerate for 10 minutes.

Heat 1 Tbsp. vegetable oil in a large Dutch oven over medium heat. Arrange half of the meatballs in a single layer in the Dutch oven. Cook for 6 to 8 minutes until meatballs are golden brown and reach 145°, turning frequently. Remove meatballs using a slotted spoon; set aside. Repeat with remaining 6 meatballs.

Increase heat to medium-high; add remaining 1 Tbsp. vegetable oil to drippings in the Dutch oven. Place bok choy, cut sides down, in Dutch oven; cook for 2 to 3 minutes or until golden brown and just beginning to wilt. Remove bok choy; set aside. Add vegetable stock and remaining 2 Tbsp. coconut aminos to Dutch oven; bring mixture to a boil. Gently add meatballs to stock mixture. Cover and cook for 10 to 12 minutes or meatballs reach 165°.

To serve, divide bok choy and meatballs among 6 serving bowls; ladle stock mixture over meatballs and bok choy. Garnish with additional green onions, if desired. Serve immediately.