Wash and chop the bok choy into bite-sized pieces, discarding the root end. Mince garlic and grate ginger. Peel and dice onion, and slice green onions for garnish.

In a large pot, heat sesame oil over medium heat. Add diced onion and sauté for 3-4 minutes until translucent and fragrant.

Stir in minced garlic and grated ginger, cooking for about 1 minute until fragrant.

Pour in 4 cups of broth, stirring to combine. Bring to a gentle boil and let simmer for a couple of minutes.

Add the chopped bok choy, reduce heat to low, and simmer for 5-7 minutes until tender.

Stir in soy sauce or tamari, adjusting seasoning with salt and pepper to taste.

Ladle into bowls and garnish with sliced green onions. Serve warm.