Rinse the prawns under cold water, pat dry, peel and remove the intestines. Finely chop the prawns and pollack.
Finely blitz the prawns and pollack in a food processor or blender.
Wash and finely chop the spring onions. Peel and finely grate the ginger. Wash the coriander, shake dry and chop the leaves. Halve the chili, deseed and finely dice.
Mix the spring onions, ginger, coriander and chili with the prawn mixture and season with salt and pepper.
Put the mixture into a piping bag and use to fill the cannelloni tubes.
Trim and finely chop the lemongrass. Wash the lime under hot water, pat dry and cut into thin slices.
Heat some water in a pan. Place half of the lemon grass and lime slices in a steamer basket.
Place about 6 cannelloni in the steaming basket. Set over the boiling water, cover and steam for 12-15 minutes. Remove the cannelloni, keep in a warm place, and cook the next portion in the same way.
Mix the vinegar with the sugar, fish sauce and sesame oil and serve with the cannelloni. Garnish with fresh coriander.