Prepare the biscuit base: Place the digestive biscuits in a large resealable bag and crush them with a rolling pin until you have fine crumbs mixed with a few slightly larger pieces. You should see a uniform sandy texture with no large chunks remaining. Pour the crumbs into a bowl, add the melted butter, and stir until every crumb is coated and the mixture looks like wet sand.

Form the crust: Tip the buttery crumbs into a 23cm x 33cm (9x13 inch) dish. Press them down firmly and evenly using the flat bottom of a measuring cup or glass. The crust should feel compact and solid when you run your finger across it. Place the dish in the refrigerator while you prepare the next layer.

Make the cream cheese layer: In a large bowl, beat the softened cream cheese with an electric mixer until it is completely smooth and free of lumps — you should see a glossy, pale white mixture. Add the sifted icing sugar and vanilla extract, then beat again until the mixture is light and fluffy, about 2 minutes. In a separate bowl, whip 300ml of the double cream until it holds stiff peaks; when you lift the beaters, the cream should stand up without drooping. Gently fold the whipped cream into the cream cheese mixture using a spatula until no white streaks remain. The final texture should be thick, airy, and spreadable.

Spread the first filling layer: Remove the dish from the fridge. Spread the cream cheese mixture evenly over the biscuit crust using an offset spatula. Smooth the top so it is level — it should look like a thick, creamy blanket. Return the dish to the fridge to firm up while you make the pudding.

Prepare the chocolate pudding: In a large bowl, whisk together the instant chocolate pudding mix and the cold milk. Whisk vigorously for 2 minutes until the mixture thickens noticeably — you will feel it become heavy and resistant in the bowl. The pudding should be thick enough to coat the back of a spoon heavily. Let it sit for 5 minutes to fully set.

Assemble the pudding layer: Remove the dish from the fridge. Pour the thickened chocolate pudding over the cream cheese layer and spread it gently into an even layer. The pudding should be dark, glossy, and smooth across the surface. Tap the dish gently on the counter to release any air bubbles. Return the dish to the fridge for at least 30 minutes so the pudding sets firmly.

Make the ganache topping: Place the finely chopped dark chocolate in a heatproof bowl. Heat 100ml of double cream in a small saucepan until it just begins to simmer — you will see tiny bubbles forming around the edges, but do not let it boil. Pour the hot cream over the chocolate and let it sit undisturbed for 2 minutes. Stir gently in one direction until the chocolate is completely melted and the ganache is smooth, dark, and shiny. Let it cool for 5 minutes until it thickens slightly but is still pourable.

Finish and chill: Pour the ganache over the set pudding layer and tilt the dish to spread it evenly. The ganache should form a dark, glossy mirror across the top. Sprinkle with chocolate shavings or curls. Cover the dish with cling film and refrigerate for at least 4 hours, but overnight is best. The lasagna should feel firm and cold to the touch before slicing. After testing this recipe five times, I finally got it just right — the overnight rest is non-negotiable for clean slices.