Prepare the vermicelli noodles according to the packet instructions. Drain, roughly chop if desired, and set aside.
Heat the oil in a large saucepan over medium heat. Add the red curry paste, garlic, and ginger, cooking for 1–2 minutes until fragrant.
Add the water, chicken stock powder, chicken, carrots, capsicum, brown sugar, lime zest and juice, coriander stalks, and half the sliced chilli. Bring to a gentle simmer and cook until the chicken is cooked through and the vegetables are just tender.
Stir in the coconut cream and the white parts of the spring onions. Season with salt and pepper to taste, then gently heat through without allowing the soup to boil.
Divide the vermicelli between serving bowls. Ladle over the soup and finish with mung bean sprouts, snow pea shoots, fresh coriander, the reserved chilli, green spring onions, and a wedge of lime.