Chocolate Tart with Salted Caramel

Flour and cocoa together need calling out: cocoa powder has no gluten in it, so swapping some flour for cocoa also makes the pastry a touch more tender, almost by accident. Use a plain flour, nothing self-raising — you don't want this base lifting or puffing, you want it flat and dense enough to carry caramel without buckling. Icing sugar rather than caster here because it dissolves into the fat without any graininess; caster would leave tiny sandy flecks in a dough this fine.

Butter: cold, and you're working it into flour, sugar and cocoa to a sandy crumb before the egg goes in — that's what a food processor is doing for you in three minutes of blending, something your hands would do slower and warmer, which is exactly the problem. Warm butter means the fat starts to properly cream rather than just coat the flour, and a creamed pastry dough bakes up cakey, not short. If you've no processor, rub it in by fingertips fast, lifting the mixture to keep air moving through it so your hands' heat doesn't melt the butter before it's distributed.

Water in the dough is there only to bring it together — add it a teaspoon at a time after the egg, because too much and you build gluten you don't want, giving you a pastry that shrinks back and toughens in the oven instead of staying crisp and short.

For the caramel, double cream specifically — its higher fat content means it won't split as readily when it hits sugar at a rolling boil the way single cream would. If a thermometer isn't to hand, judge it by colour and behaviour instead: it should be the colour of dark honey, not yet the colour of strong tea, and a drop in cold water should form a soft, pliable ball you can squash flat, not a hard bead that snaps. Soft brown sugar alongside the caster sugar is for depth more than mechanism — molasses in it rounds the caramel out so it isn't just sweet, it's got a back note like toffee. No glucose syrup in the cupboard? Golden syrup does the same anti-crystallising job, just slightly sweeter and darker in flavour. The half teaspoon of salt stirred in after cooking, not before, is what makes this a salted caramel rather than a plain one — adding it earlier would have no different effect on the chemistry, it's simply traditional to season at the end once off the heat, when you can taste and adjust.

Dark chocolate for the ganache — go for something you'd actually eat off a bar, because with only cream to dilute it, every flaw or blandness in cheap chocolate shows up directly in the slice. Chop it finely, not because of tradition, but because small pieces melt evenly from the heat of the poured cream alone; a few big chunks sitting in a bowl under barely-boiled cream just won't get there and you'll end up microwaving it, risking the chocolate seizing into a grainy mess instead of staying glossy.

And then there's patience, which is really the secret ingredient of the whole tart — you cool the caramel to room temperature before it goes in, you cool the ganache before it goes on, and you give the finished tart a genuinely long chill, the better part of an afternoon, because this is a dessert built in temperature-dependent layers: rush any cooling stage and the layers above either slide or melt into the one below, and you've made a chocolate caramel soup instead of a tart. A wide domestic oven and a 24cm tin off a supermarket shelf will do this perfectly well — nothing here asks for a kazan or anything you don't already have, just time you have to actually give it rather than skip.

This feeds ten in thin wedges, which given how rich it is, is about right — it's not a dessert anyone needs a large slice of, any more than you'd want a large slice of fudge.