Prepare the Coffee Soak: Brew your strong coffee and allow it to cool completely. If using the coffee syrup, stir it in now. The liquid should be at room temperature — hot coffee will make the biscuits soggy instantly.

Make the Mascarpone Cream: In a large, clean bowl, whisk the egg yolks with the caster sugar until the mixture is pale, thick, and leaves a ribbon trail on the surface when you lift the whisk. This should take about 3-4 minutes and will look a light, lemony yellow.

Add the Mascarpone: Gently fold the mascarpone and vanilla extract into the yolk mixture using a spatula. Fold until just combined. Do not overmix, or the cream can become thin. The texture should be smooth, thick, and luxurious, with no white streaks.

Whip the Egg Whites: In another perfectly clean, dry bowl, whisk the egg whites until they form stiff peaks. You should be able to turn the bowl upside down without the whites moving. They should look glossy and feel firm, not dry.

Fold the Meringue: Take a large spoonful of the whipped egg whites and stir it into the mascarpone mixture to loosen it. Then, gently fold in the remaining whites in two additions. Use a figure-of-eight motion to keep the air in. The final mixture will be light, airy, and billowy, almost like a soft cloud.

Assemble the First Layer: Quickly dip each ladyfinger into the cooled coffee. Count to two — don't let them soak, or they will collapse. Arrange them in a single layer in your serving dish. The biscuits should be snug, covering the entire base.

Layer and Repeat: Spread half of the mascarpone cream evenly over the first layer of biscuits. Use a palette knife or the back of a spoon to create a perfectly flat surface. Repeat with another layer of dipped biscuits and the remaining cream. The top should be smooth and even.

Chill and Set: Cover the dish with cling film and refrigerate for at least 6 hours, but preferably overnight. This resting time is crucial. The biscuits will soften to a cake-like texture, and the flavours will meld into a harmonious whole. The top will feel firm to the touch.

Finish and Serve: Just before serving, use a fine-mesh sieve to dust the top generously with cocoa powder. For a restaurant touch, add a few dark chocolate shavings. Slice cleanly with a sharp knife, wiping the blade between cuts for perfect portions.