Thinly slice the spring onion. Crush or finely chop the garlic. Peel and finely grate the ginger. Halve the carrot lengthwise, then thinly slice on an angle. Trim the broccoli stem and coarsely chop. Cut the broccoli head into small florets. Drain and rinse the corn.
Step 2 — Make stock
Put the stock powder in a heatproof jug, add 1L (4 cups) boiling water and stir to dissolve.
Step 3 — Cook vegetables
Heat 2 tsp oil in a large saucepan over medium-high heat. Cook the spring onion, garlic and ginger, stirring, for 1 min or until fragrant. Add the stock and bring to a simmer. Add the carrot and broccoli stem, reduce the heat to medium-low and cook, covered, for 5 mins.
Step 4 — Cook dumplings
Bring the soup to the boil, add the dumplings and broccoli florets, reduce the heat to medium and cook, covered, for 4 mins or until tender.
Step 5 — Make soy seasoning
Meanwhile, combine the sesame oil, 3 tsp soy sauce, 1 tsp sugar and ½ tsp white vinegar in a bowl.
Step 6 — Get ready to serve
Stir the corn and soy seasoning into the soup, then season with pepper. Divide the soup among bowls. Scatter with the sesame seeds and a pinch of chilli flakes*, if desired, to serve.