This lovely dish couldn't be easier or cheaper.
We had some egg yolks left over after making some coconut macaroons (2 egg whites, 160g dessicated coconut, 100g sugar - whisk then put some blobs onto some baking paper and bake in the oven at 180 for 12ish minutes) which were, well still are in fact, delicious. With the egg yolks we made some mayo. Homemade mayo really will put you off shop bought for good.
If you want arms like Popeye then whisking mayonnaise is the way forward. But if you want to make your life a lot easier then a blender comes in very handy. All it takes is 2 egg yolks, a teaspoon of dijon mustard (and some english mustard if you fancy), a dash of white wine vinegar and some oil. We tend to use normal vegetable oil (which more often than not is rapeseed oil) so that the mayo doesn't take on a taste of oil, but some recipes I've seen suggest olive oil. So use whatever takes your fancy.
Put everything except the oil into a blender and give it a couple of short bursts, then switch to constant and start trickling in the oil. It'll take quite a bit, something like 150-200ml. It's done when you have a thickish pale yellow sauce. It will need a little bit of seasoning, which is best done at the end. If you're using pepper, use white rather than black to prevent very visible black bits in the mayo.
We had a mackerel in the freezer and felt like having a light Sunday lunch, so we thought we'd have it with a potato salad made with our homemade mayo.
It doesn't take a lot of explaining really. We boiled some new potatoes, cut them in half and then mixed them with some mayo, some chopped gherkin and some fresh mint for a very tasty potato salad. We simply topped that with a grilled mackerel fillet, and there you have it. A very rewarding tea for very little effort.