Flounder Fillet with Tartare Sauce and Potatoes

Start with the potatoes, because they're the slow part and a British kitchen already knows this rhythm from Sunday roast — the spuds go in before anything else is even thought about. Skin on, cut into wedges rather than small cubes: more surface for crisping, less surface lost to peeling, and the skin itself holds the wedge together so it doesn't collapse to mush at 200°C. Turning them "a few times" isn't fussing — it's preventing the side touching the tray from frying in its own steam while the top stays pale. Doneness here is a fork going in without resistance and a crust you can hear when you turn them, not a timer going off.

Olive oil for the potatoes: any oil that can take real oven heat without smoking or complaining works — a flavourless vegetable oil, sunflower, even light rapeseed, which is arguably more at home in a British larder than olive oil ever was. Olive oil is doing nothing magical here except not fighting the potato's own taste.

Flounder is a bottom-feeding flatfish — thin body, two small fillets off each side, delicate flake, forgiving price. If you can't get it, any other flat fish does the same job: plaice, sole, dab. The flatness is the point, not the species — it fries evenly in minutes because there's no thick centre lagging behind a cooked edge, the way there is in a cod loin. Don't substitute a thick round fillet without rethinking the frying time; it's a different animal on the pan.

The egg-then-flour sequence is the oldest trick in frying and it has a real reason: egg is sticky and wet, flour is dry and needs something to cling to. Reverse it — flour then egg — and you get a gluey, uneven mess, because the egg just slides off dry flour instead of binding to bare, slightly damp fish. Butter plus olive oil in the pan, not butter alone: butter alone burns before the fish is properly coloured because its milk solids scorch at a fairly low heat; the oil raises the point at which the fat starts complaining, and the butter still gives you that nutty smell and better browning than oil could manage on its own. "Medium heat" is really: hot enough that the crumb starts fizzing and colouring within the first thirty seconds the fillet touches the pan — if it sits there pale and silent, the pan wasn't hot enough and the fish will stew in fat instead of crisping.

The tartare sauce is mayonnaise and crème fraîche as the base — fat and tang, cut by capers and gherkins for salt and sharpness, mustard for a background heat you won't taste directly but will miss if it's gone, lemon zest and juice to lift the whole thing off the plate. If you've no crème fraîche, soured cream or even thick natural yoghurt stands in — anything with real acidity and body, not thin pouring cream, which just dilutes without adding anything back. Some say tartare sauce is "just mayonnaise with bits in" — no, because the capers and gherkins aren't garnish, they're the acid that stops the whole plate tasting of fried batter and fat.

The herbs — dill, parsley, chives — aren't decorative either; fresh and finely chopped, they bring a green, slightly bitter freshness that mayonnaise-based sauces always need or they sit heavy. Dried herbs here would be a false economy: dried dill in particular loses almost all its character and leaves you with dust, not flavour. Cucumber sticks and lemon wedges on the side do the same job raw that the sauce does blended — more acid, more crunch, because a plate of fried fish and roast potato, left alone, is entirely fat and starch and needs something cold and sharp fighting back.