1. Melt the butter in a large saucepan then fry off the onions and garlic until soft. Sprinkle with salt to speed up the process.
2. Add the vegetable stock and the diced potatoes to the pan then bring to the boil, simmer for approximately 10 minutes, or until the potatoes are just cooked.
3. Meanwhile, pour the milk into a separate deep frying pan and bring to the boil. Carefully place the haddock fillets in the milk and poach for 5 minutes. Drain, keeping the milk to one side and then flake the fish.
4. Add the fish and milk to the original saucepan. Put in the sweetcorn and parsley then simmer altogether for a couple more minutes. Season to taste and serve with some crusty bread.