Warm the cream and milk: Pour the double cream, whole milk, and golden caster sugar into a medium saucepan. Place over a medium heat and stir gently with a wooden spoon. You’re looking for small bubbles to appear around the edge of the pan — that’s when the liquid is hot but not boiling. The mixture will look pale and slightly frothy. Do not let it come to a rolling boil, or the cream might split.

Melt the chocolate: While the cream warms, put the finely chopped dark chocolate into a heatproof bowl. The chocolate pieces should be no bigger than a pea so they melt evenly. When the cream mixture is hot, pour it over the chocolate. Let it sit untouched for one minute — this allows the heat to begin melting the chocolate from the bottom up. The air will smell deeply of cocoa.

Whisk until glossy: After the minute is up, whisk gently in one direction. You’ll see the mixture transform from a pale, speckled liquid into a dark, glossy ganache. Continue whisking until every last piece of chocolate has dissolved and the mixture looks like liquid velvet. It should coat the back of a spoon thickly.

Temper the egg yolks: In a separate small bowl, lightly beat the egg yolks with a fork until they are uniformly yellow and slightly thickened. While whisking the chocolate mixture continuously, drizzle the egg yolks into the pan in a slow, steady stream. This step is crucial — adding the yolks too quickly can scramble them. The mixture will thicken noticeably and become even glossier, almost like a pudding.

Cook gently: Return the saucepan to the lowest possible heat. Stir constantly with a wooden spoon or heatproof spatula for about two minutes. You’ll feel the mixture thicken against the spoon, and it will start to steam gently. Do not let it bubble. The texture should be like a thick custard that coats the spoon heavily. When you drag your finger across the back of the spoon, it should leave a clean trail.

Strain and pour: Set a fine-mesh sieve over a large jug or a bowl with a pouring lip. Pour the chocolate mixture through the sieve to catch any tiny bits of cooked egg. Press it through with the back of a spatula. The strained mixture will be impossibly smooth and silky. Divide it evenly among six small glasses, espresso cups, or small ramekins. Tap each glass gently on the counter to release any air bubbles.

Chill until set: Place the pots in the refrigerator, uncovered, for at least 30 minutes. After 30 minutes, the surface should be firm to the touch but still wobbly underneath. For a firmer, mousse-like texture, chill for at least 4 hours or overnight. The surface will look matte and set like a dense pudding.

Finish and serve: Just before serving, sprinkle a tiny pinch of sea salt flakes over each pot. The salt crystals will glisten against the dark chocolate surface. If you like, top with a single raspberry, a few chopped hazelnuts, or a tiny dollop of whipped cream. Serve straight from the fridge; they are best enjoyed cold.