Beef burgers, meh, I can take them or leave them. Mostly I like them for the trimmings. A fried fish sandwich, though, is something else. A juicy mackerel fillet, cooked until the skin is crisp, slapped in a bun and anointed with tartare sauce with an unorthodox hit of horseradish … well, now I’m salivating.
I get slightly irritated by burgers that are so tall you have to eat them with a knife and fork. There’s no denying that they look better in photographs, but you should be able to eat a burger with your hands without spilling the contents or having to deconstruct the dratted thing. So build yours however you please, eat the salad on the side if you like, but the gherkins and sauce are non-negotiable in our house.
I like my tartare sauce stiff with pickles, and in this instance with a good snap of horseradish. I suggest you start with the smaller quantities of cornichons and capers listed, taste, and add more if required. As for the horseradish, if you hate it the idea of it, leave it out. If you love the stuff, grate in more but remember this is meant to be a spiky tartare, not a horseradish sauce you’d eat with roast beef.
Freshly grated horseradish is best but it’s hard to get if you don’t grow it. I haven’t tried this recipe with the bottled stuff. My instinct would be to leave it out and just enjoy a properly made tartare sauce for its own sake, but it’s up to you. I prefer sweet pickled cucumbers in the sauce rather than brined gherkins, but again, it’s a matter of preference.
Finally, I think it’s worth making the tartare sauce from scratch but for nearly instant gratification, mix good shop-bought mayo with the ingredients below.
2 mackerel fillets, skin on
1 tbs plain (all purpose) flour
Salt and pepper
Oil, for frying
2 burger buns
For the tartare sauce:
1 egg yolk
1/2 tsp Dijon mustard
1/4 tsp salt
50ml olive oil
75 ml sunflower oil (or make it 50:50 if you prefer)
A good squeeze of lemon juice
1 heaped tbsp capers, drained and roughly chopped (or more, to taste)
1-2 heaped tbsp cornichons, drained and diced small (ditto)
1 tbsp freshly grated horseradish (ditto)
1 heaped tbsp fresh parsley, chopped
Make the tartare sauce: break the egg yolk into a bowl and stir in the mustard and salt. Add the oil, one drip at a time to start with, whisking constantly. Once the emulsion forms you can begin adding it in a thin stream. If you prefer to use a food processor, add the oil, drop by drop to start with, through the funnel. If by some mischance the mixture splits (and it’s happened to all of us), break a fresh egg yolk into a clean bowl and add the curdled mixture drop by drop as before.
When all the oil has been amalgamated the mayo will look like a thick ointment, but don’t worry, it’ll be thinned by the lemon juice and pickles.
Stir the lemon juice into the mayo. Chop the pickles and parsley and add to the bowl. Taste and adjust the salt content as necessary. Stir in the grated horseradish, if using, a teaspoonful at a time until the sauce has the bite you prefer. Cover and refrigerate.
Prep any remaining garnishes; slice tomatoes and gherkins, wash and dry lettuce, make ready any side dishes and toast the cut side of your halved bread buns, because from here it all comes together very quickly.
Put a large frying on the hob and add a couple of tablespoons of oil. Turn the heat high.
Spread the flour on a large plate and season with a little salt and pepper. Cut each mackerel fillet in half, season lightly, and dust each piece through the flour, shaking off any excess.
Put the fish in the hot oil, skin side down, and turn the heat down to medium-hot. Press the fillets gently with a spatula to stop them curling up and to keep the skin in contact with the pan. Fry for two to four minutes, depending on thickness, then turn the fish over and remove from the heat. The residual heat will be sufficient for it to finish cooking.
Then all you need to do it assemble your sandwich, with its trimmings, in whatever order pleases you best.