Whisk the dry base: In your saucepan (off the heat), whisk together the caster sugar, cornflour, cocoa powder, and salt. You’re looking for an even, speckled brown mixture with no visible lumps of cornflour — it should feel powdery and fine when you rub a bit between your fingers.

Add the milk slowly: Pour about 100ml of the milk into the dry mixture and whisk until you have a thick, dark paste. The paste should be smooth and glossy, similar to a thin chocolate spread. This step prevents lumps later.

Incorporate the remaining milk: Gradually pour in the rest of the milk, whisking constantly. The mixture will thin out to the consistency of a regular milkshake — pale brown and very liquid. Don’t worry, it will thicken beautifully.

Cook over medium heat: Place the saucepan over medium heat and stir constantly with a wooden spoon or spatula. After about 3–4 minutes, you’ll notice the mixture starting to steam gently — that’s your cue that it’s heating through. Keep stirring, scraping the bottom and corners of the pan.

Watch for the first bubbles: Around the 6-minute mark, you’ll see lazy bubbles breaking the surface. The mixture will suddenly begin to thicken; you’ll feel the drag on your spoon. Don’t walk away — stirring is essential now.

Boil for one full minute: Once the pudding is bubbling steadily across the entire surface (big, slow bubbles), set a timer for exactly 60 seconds. The mixture will have the texture of thin custard at this point. Stir constantly — you’ll see it transform to a thick, glossy pudding that leaves a clean trail when you drag your spoon across the bottom of the pan.

Remove from heat and add the good stuff: Take the pan off the heat immediately. Drop in the chopped dark chocolate, butter cubes, and vanilla extract. Stir gently until everything melts into the hot pudding — the chocolate and butter will create a dark, satiny sheen. The smell at this stage is pure indulgence, rich and slightly toasty.

Finish with cream if using: If you’re adding the double cream, pour it in now and stir until fully incorporated. This step is optional, but it gives the pudding an extra velvety mouthfeel that feels truly luxurious.

Divide and cool: Pour the pudding into four individual ramekins or a single serving dish. The texture should be thick enough to mound slightly before settling flat. Let them sit at room temperature for 10 minutes — a thin skin will form on top, which some people love. You can cover them with cling film (pressing it directly onto the surface to prevent a skin forming) and refrigerate for later, or serve warm.