Finely dice the carrot, shred the green-cabbage, and finely chop the French beans and spring onion, keeping the spring onion whites and greens separate.

Finely chop the garlic and ginger so they are ready to sauté into the base of the soup.

Melt the butter in a saucepan and sauté the chopped garlic, ginger, and spring onion whites until fragrant and lightly softened, without letting them brown.

Pour in the vegetable stock, stir to combine with the sautéed aromatics, and bring the soup to a rolling boil.

Add the diced carrot, shredded green-cabbage, and chopped French beans to the boiling stock and simmer until the vegetables are tender but still have a slight bite.

Stir in the salt, freshly cracked black pepper, and soy sauce if using, mixing well so the seasoning is evenly distributed through the broth.

Turn off the heat, squeeze in the lemon juice if using, and taste to adjust the salt or pepper before serving.

Let the soup sit for a couple of minutes so the flavors settle, then ladle into bowls and garnish with the reserved spring onion greens.