4 egg yolks
1/3 cup (64g) caster sugar
1/4 cup milk
250g packet savoiardi or sponge fingers
1 1/2 cups cold coffee
Beat egg yolks and sugar in a heatproof bowl until light and creamy. Add milk and beat until combined.
Place bowl over a pan of simmering water. Stir over heat until thickened; allow to cool.
Add mascarpone to mixture; stir until combined. Beat egg whites until soft peaks form; fold into mixture.
Dip savoiardi biscuits quickly into coffee - they should be moist but not soggy. Place a quarter of the biscuits over base of a 1.5L serving dish or a paper-lined loaf pan. Spread with one-third of the mascarpone mixture. Repeat layering with remaining biscuits and mascarpone.
Cover and refrigerate at least 6 hours, preferably overnight. Sift cocoa over top to serve.