• Warm the milk in a shallow pan over a low heat. When the milk is steaming, add the haddock and poach gently for 4 to 5 minutes until the fish starts to turn opaque. Remove to a plate or board using a slotted spoon, then strain the milk through a sieve into a jug. Set aside. Flake the fish into small pieces, discarding any skin and bones.
• Fry the chorizo in a dry frying pan over a medium heat for about 5 minutes, until crisp. Remove the chorizo using a slotted spoon and transfer to the plate with the fish.
• Melt the butter in the same pan and, once foaming, add half of the flour, stirring until you have a smooth paste. Slowly add the strained poaching milk, stirring continuously until the sauce has thickened, then add the cheese and some freshly ground black pepper (you shouldn’t need any salt). Remove from the heat and set aside to cool for 10 minutes, then add the chorizo, haddock, chives and parsley.
• Tip the mixture onto a plate or into a baking dish, spreading it out to help it cool quickly. Cover the surface with a sheet of baking paper, then chill for 2 hours, or overnight.
• Roll the mixture into cherry-tomato-sized balls using dampened hands (you’ll make about 35 in total). Tip the remaining flour onto a plate, then beat the eggs in a shallow bowl, and tip the breadcrumbs onto a second plate. Roll each ball in the flour, followed by the egg and finally the breadcrumbs. Transfer to a baking tray lined with baking paper, well spaced apart. NOTE: the croquettes will keep chilled for up to a day or frozen for a month. Defrost thoroughly in the fridge overnight before cooking.

For the beer and mustard mayo (optional):

• If you’re serving the mustard and beer mayo with the croquettes, simply mix all of the ingredients together in a small serving bowl and set aside until you’ve cooked the croquettes.

Fry the croquettes:

• Half-fill a deep pan with oil and heat to 180C, or until a cube of bread sizzles and starts to brown when dropped in. Fry batches of five or six croquettes for 5 to 6 minutes until deeply golden, turning halfway through. Remove to a plate lined with kitchen paper to drain, then sprinkle with sea salt flakes and extra chives. Serve hot with the mustard and beer mayo, if you like.