First make the lemon mayonnaise. Whizz the egg yolks, vinegar, mustard and lemon juice in a food processor. With the motor still running, slowly pour in the oil through the feed tube, processing until the mayonnaise is emulsified and thickened. If it’s too thick, thin it slightly with some warm water. Season with salt and white pepper and refrigerate until needed.
When you’re ready to eat, slowly heat the oil in a deep fat fryer until it reaches 180°C.
While the oil is warming up, quickly whisk together the batter. Put the flours and bicarbonate of soda into a bowl. Season with salt and cayenne pepper. Pour in the sparkling water and whisk to form a loose batter.
Dust the pieces of monkfish in some semolina flour and then dip them in the batter. Fry for 3-4 minutes or until the batter is crisp and golden. Don’t crowd the fryer. You may need to do this in batches – make sure you let the oil come back up to temperature between batches. Use a slotted spoon to remove the monkfish from the oil. Drain on kitchen paper and season with salt and cayenne pepper, to taste.
Serve with the lemon mayonnaise, garnished with lemon zest.