Bitter Chocolate Semifreddo (The No-Churn Italian Frozen Mousse)

Line a 900 g (2 lb) loaf tin with two sheets of plastic wrap laid crosswise, leaving generous overhang on all sides. Place in the freezer while you prepare the base.

Melt the chocolate in a heatproof bowl set over a pan of barely simmering water, stirring until smooth. Remove from heat and cool until warm to the touch — around 40–45°C (104–113°F). Too hot and it will melt the cream or scramble the yolks when combined.

Whip the cream in a chilled bowl to soft-medium peaks — it should hold a gentle shape when you lift the whisk but still look glossy and billowy, not stiff or dry. Overwhipping here is the most common failure point. Refrigerate until needed.

In a clean, grease-free bowl, whisk the egg whites with the lemon juice and salt until frothy. Add 60 g of the sugar in a steady stream and beat to stiff, glossy peaks. Set aside.

In another bowl, beat the egg yolks with the remaining 60 g sugar until pale, thick, and at ribbon stage — lift the whisk and drizzle the mixture; it should hold a ribbon on the surface for 3–4 seconds.

Stir the espresso powder and rum into the cooled chocolate until combined, then fold in the yolk mixture with a spatula until smooth.

Add the whipped cream to the chocolate base in two additions. Fold with a cut-and-sweep motion — spatula down the centre, up the sides — until just combined. No stirring or beating.

Add the egg whites in three additions, folding gently after each. Stop as soon as no white streaks remain — aggressive folding now deflates the foam and produces a dense, icy slab.

Pour the mixture into the prepared tin, smooth the surface, and fold the plastic wrap over the top to cover completely. Freeze for a minimum of 6 hours, or overnight.

To serve, unwrap the top, invert onto a chilled board, and peel away the plastic wrap. Rest at room temperature for 5 minutes. Run a long knife under hot water, wipe dry, and slice cleanly. Finish with a dusting of cocoa powder, a scatter of cacao nibs, or a pinch of flaky salt.