Grease a 24cm (9½in) springform pan; line base and side with baking paper. Wrap a 9cm (3¾in) round ramekin (or other straight-sided round dish) with a double layer of plastic wrap. Grease plastic; place in centre of pan.

Combine coffee and the boiling water in a small jug. Stir to dissolve, then stir in liqueur. Cool.

Beat cream and icing sugar in a large bowl with an electric mixer until soft peaks form. Fold in mascarpone, coffee beans and ¾ cup of the macadamias, then fold in coffee mixture until just combined.

Spoon mixture into prepared pan; smooth the top. Freeze for 4 hours or until firm.

Meanwhile, make biscuit base. Process the biscuits and malt balls until coarse crumbs; add butter; process briefly to combine.

Press biscuit mixture over top of ice-cream to form a smooth surface. Freeze overnight.

To serve, remove ramekin and release the side from the pan (if necessary, rub outside of cake pan with a hot damp cloth). Place inverted plate on top of ice-cream and turn over. Remove the bottom of the pan and cover with a serving plate; turn over. Top ice-cream with remaining macadamias, chocolates, truffles and extra chocolate-coated coffee beans. Dust wreath with a little sifted cocoa powder, if you like.