Mackerel With Parmesan Crust, Horseradish And Pea Sauce And Roast Mushrooms

There’s a supposedly unbreakable rule in Italian cooking that says you are never meant  to mix seafood and parmesan although like many of these things it appears to be entirely arbitrary; I read an article about this by Heston Blumenthal years ago but only recently did I look more closely behind the science of why the two are actually a very good combination. The main reason is due to the compounds present in parmesan (glutamate) and fish (inosinate): when these two combine they have a synergistic effect and this increases the perception of umami by a factor of eight.

After discovering mackerel has some of the highest concentrations of inosinate of any fish I got the idea for adding a parmesan crust as a way of combining the two ingredients. This is one of the few times I would recommend using a non-stick pan because it really helps here as the cheese often sticks to the surface when browning and this can make it difficult to flip the fish.

There is also a third compound called guanylate which enhances the umami synergy even more and is very prevalent in mushrooms  (especially when dried) so I decided to add some of those too. The process of drying increases the amount of guanylate significantly but I didn’t think the texture would be appropriate and instead I chose to slow roast fresh portobellos at a low temperature in the oven to cook them and partially dry them out as well.

Finally, a word of warning about horseradish is that its pungent flavour is dissipated by heat: make sure to add it to the sauce just before you serve for maximum impact.

Serves: 2

For the mackerel
50g flour
1 egg lightly beaten
50g breadcrumbs
50g parmesan
2 mackerel fillets
15ml rapeseed oil

For the sauce
200ml creme fraiche
100ml chicken stock
100g of peas
15g freshly grated horseradish

For the mushrooms
25ml olive oil
2 large portobello mushrooms


  1. For the mushrooms, preheat the oven to 100°C.
  2. Season the mushrooms generously, pour over the olive oil and cook for 6 hours.
  3. For the sauce, cook the peas in the stock with a pinch of sugar and salt.
  4. When cooked, remove the peas and reserve the cooking liquid.
  5. Place the the creme fraiche and the stock in a pan and reduce by a third.
  6. Add the peas to heat them through and just before serving season to taste and add the horseradish.
  7. For the mackerel, mix the breadcrumbs and the parmesan together thoroughly.
  8. Coat the skin side of one of the fillets in flour, shaking off any excess.
  9. Dip the floured side of the fish into the beaten egg and then dip the same side into the breadcrumb mixture whilst ensuring there’s an even coating over the skin.
  10. Repeat for the other mackerel fillet.
  11. Place a pan on a medium heat to warm up and then add the oil.
  12. Place the fillets skin side down in the pan for around two minutes or until the coating has browned.
  13. Season the uncoated side of the fish lightly with salt and after taking the pan off the heat turn the fillets over.
  14. To plate, cut the mushroom in to large slices and place in the middle, lay the mackerel skin side up on the mushrooms and top with the horseradish sauce.

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