Line a 450g/1lb loaf tin with cling film, making sure you have enough overhang to cover the top later.
Whip the cream until thick but still soft.
Chop the chocolate very finely so that you have a pile of dark splinters, and fold them into the cream, along with the liqueur.
Now, using brute force, crumble the meringue nests and fold these in, too.
Pack this mixture into the prepared loaf tin, pressing it down with a spatula as you go, and bring the cling film up and over to seal the top, then get out more cling film to wrap around the whole tin. Freeze until solid, which should take around eight hours or overnight.
About an hour before serving, make the chocolate sauce. Pour the cream into a saucepan and add the tiny bits of chocolate. Put over a gentle heat and whisk as the chocolate melts, taking the pan off the heat once the chocolate is almost all melted. If the mixture gets too hot, the chocolate will seize, whereas it will happily continue melting in the warm cream off the heat.
Add the liqueur, still off the heat, and whisk again to amalgamate the sauce completely. Pour into a jug, whisking every now and again until it cools to the desired temperature. If you feel the sauce has thickened too solid, then stand the jug in a bowl of warm water for a few minutes, whisking frequently, before pouring. Or I whisk in a shot - about two tablespoons - of hot espresso.
To serve the gelato cake, unwrap the outer layer of cling film, then unpeel the top and use these bits of long overhanging wrap to lift out the ice-cream brick. Unwrap and unmould it onto a board and, using a sharp, heavy knife (dipped in hot water between each slice) cut the frozen meringue cake into slabs to serve. I like to zig-zag a little chocolate sauce over each slice and sprinkle a few raspberries alongside on each plate.