I made this with the leftover pil-pil sauce and cooking oil the last time I made bacalao al pil pil (which is salt cod in a warm mayonnaise). The original recipe has 500 ml of olive oil, of which only half is used in the pil pil sauce. So you already have 250 ml of cod-flavoured olive oil going spare. On top of that, there will probably be some leftover pil pil sauce. When I saw that I had getting on for 350 ml of top quality olive oil about to go to waste, I suggested to Gemma that I make it into mayonnaise. She looked at me as if I was a bit mad, but I made it anyway.
leftover olive oil and pil pil sauce from bacalao al pil pil
Put the olive oil and leftover sauce in a bowl, and whisk gently until it liaises to form a light mayonnaise.
This made a really good mayonnaise, which was quite light and had a delicate flavour of cod. I knew that nobody else in my family would knowingly eat it, but I tricked them by using it to dress some spaghetti with salt cod, chick peas and green peppers, which they all ate happily. (I had an extra serving of mayonnaise on top of mine.) They will only realise they ate the mayonnaise too if they read this blog entry!
As I was writing this entry, I thought I would have a quick search to see if anyone else makes salt cod mayonnaise. I came across a reference to a restaurant in Dublin called Pichet which sometimes has it on their menu, but no actual recipes, so I think this counts as a culinary googlewhack.