Heat the oil in a wide non-stick pan with a tight-fitting lid. Fry the onions and potatoes for about 5 mins, or until starting to soften. Add the peppers, courgettes, tomatoes and garlic, then stir in the vinegar, if using, the bouillon and 200ml water. Bring to a simmer, cover and cook for 25 mins, or until the peppers and courgettes are very tender (if your pan doesn’t have a tight-fitting lid, wet a sheet of baking parchment and place over the stew before covering – this helps keep in the juices).

Add the hake fillets, mussels and prawns, then cover and cook for 5 mins more, or until the fish flakes easily when tested with a fork. Scatter over the parsley and serve.