Preheat the oven to 200˚C.
Clean the mussels and discard any that don’t close when tapped sharply.
Place the potatoes in a saucepan filled with salted water and bring to the boil. Simmer for 15 -18 minutes until softened. Remove from the heat and drain any excess water. Transfer on a baking tray and drizzle with some oil. Season well with salt and pepper and some cayenne pepper. Roast in the oven for 15 minutes until lighly coloured.
In the meantime, Pour the beer into a wide saucepan, add the mussels, shallots, sweet corn, garlic, cayenne pepper and bring to the boil over a high heat. Reduce the heat and simmer covered for 4-5 minutes until the mussels open. Add the prawns and continue cooking for a further 4-5 minutes.
Remove from the heat check the seasoning and serve immediately in a platter lined with news paper or parchment paper and topped with potatoes wedges.
Sprinkle with the herbs and extra spices if desired, serve with a wedge of lemon!