Prepare the chocolate ganache layer: Place the finely chopped dark chocolate in a heatproof bowl. In a small saucepan, warm 300ml of the double cream over medium heat until it just begins to steam and small bubbles form around the edge—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 mixture becomes glossy, smooth, and completely homogenous, with a thick, velvety texture that coats the back of a spoon. Set aside to cool for 15 minutes.

Whip the mascarpone cream: In a large mixing bowl, combine the mascarpone cheese, the remaining 300ml double cream, caster sugar, and vanilla bean paste. Using an electric mixer on medium speed, whisk until soft peaks form—the mixture should be thick enough to hold its shape but still feel luscious and airy. You’ll know it’s ready when you lift the beaters and the cream folds over gently without collapsing. Be careful not to overwhip, or the cream will turn grainy.

Prepare the coffee dip: Pour the cooled strong black coffee into a shallow dish. If you want a deeper flavour, add a pinch of instant coffee granules and stir until dissolved. The liquid should be at room temperature—if it’s too hot, the sponge fingers will turn to mush.

Layer the sponge fingers: Working one at a time, dip each sponge finger into the coffee for no more than 2 seconds per side—you want them lightly moistened, not saturated. Arrange them in a single layer at the bottom of your serving dish or individual glasses. Press them gently so they form an even base. You should hear a faint, soft squish as they settle.

Add the first ganache layer: Spoon half of the cooled chocolate ganache over the sponge fingers, spreading it evenly with a small offset spatula or the back of a spoon. The ganache should be thick and fudgy, with a dark, glossy sheen that looks like molten chocolate silk. Let it settle for 1 minute.

Add the mascarpone cream layer: Dollop half of the whipped mascarpone mixture on top of the ganache, then spread it gently to the edges. The cream should be pale ivory in colour, with a billowy, cloud-like texture. Use a circular motion to create gentle swoops on the surface—this adds visual interest when the trifle is sliced or viewed through glass.

Repeat the layers: Dip and arrange another layer of sponge fingers, then top with the remaining ganache, and finish with the remaining mascarpone cream. Smooth the top layer of cream into a neat, even surface. The trifle should now have five distinct stripes when viewed from the side: sponge, ganache, cream, sponge, ganache, cream.

Chill and set: Cover the dish tightly with cling film and refrigerate for at least 4 hours, or overnight. During this time, the layers will meld together and the sponge fingers will soften into a cake-like texture. You’ll know it’s ready when the top feels firm to the touch and a spoon glides through the layers without resistance.

Finish and garnish: Just before serving, dust the top generously with cocoa powder through a fine-mesh sieve. Scatter over the dark chocolate shavings and, if using, a few fresh raspberries or strawberries. For a final restaurant touch, sprinkle a tiny pinch of sea salt flakes over the top—it cuts through the richness and makes the chocolate flavour sing.