Lightly oil, then line the base and sides of a 20cm loose bottom cake tin with strips of plastic acetate (or waxed paper).

Crush the biscuits in a bag to a fine breadcrumb consistency, then transfer to a bowl. Stir in melted butter, then cover the base of the cake tin with the biscuit crumbs, pressing down with the back of your hand. Refrigerate the base.

Whip 200ml of the cream and set it aside.

In a heatproof bowl sitting above a saucepan of lightly simmering water, add the remaining 225ml of pouring cream and 400g chopped chocolate, and stir until smooth. Let the chocolate cream cool for three minutes before whisking in the egg yolks.

Using a large bowl, whisk the egg whites with an electric mixer to soft peaks, then add the sugar and continue whisking, until glossy. Stir in the orange zest. Take a spoon of egg white and stir it into the chocolate to loosen it, then use a folding motion to combine the egg whites and chocolate. Lastly, fold the whipped cream into the mixture until no streaks remain, before spooning the mixture over the biscuit base. Level the surface and chill for four hours.

For the chocolate icing, place the chocolate in a bowl and set it aside. In a small saucepan, bring the cream to a simmer with the liquid glucose. Pour the scalding cream over the chocolate and stir to a smooth glaze.

Release the torte from the tin, and peel away the lining. Spoon the icing over the top and sides of the chilled torte (place the torte on a wire rack, with parchment underneath to catch any spills). Refrigerate.