Lightly chill four serving glasses in the freezer for around 10 minutes—just enough to keep the gelato perfectly composed as you assemble.
In a small bowl, whisk the mascarpone with the sugar until smooth, pale, and softly aerated. If using, fold in the coffee liqueur, allowing it to perfume the cream with gentle warmth.
Divide the gelato between the glasses, shaping each scoop with care so it sits neatly, ready to receive the layers that follow.
Spoon over a generous quenelle of the mascarpone cream, letting it fall naturally into soft, elegant folds.
Brew the espresso fresh. While still hot and aromatic, pour a measured shot over each glass just before serving, allowing it to cascade through the layers and gently soften the gelato beneath.
Finish with a fine veil of cocoa, sifted delicately over the surface. Add a savoiardi or a scattering of dark chocolate shavings, if desired, for a final flourish.
Serve at once—while the contrast of temperature and texture is at its most exquisite—inviting each spoonful to capture the full, fleeting harmony of espresso and cream.