Bring the ice cream out of the freezer 10 mins before assembling so it's just softening. Layer half of the trifle sponge in a cling film lined tin (20x20cm) making sure there is overhang.

Tip the ice cream into a mixing bowl and combine quickly, drizzle half the rum over the sponge and then top with half of the ice cream. Flatten with a spatula then repeat the process with the remaining sponge, rum and ice cream.

Smooth the top and sprinkle with the hazelnuts, then get it back in the freezer as soon as possible. Freeze for at least 4 hours until set, preferably overnight.

When it's time to serve, take out of the freezer 5-10 mins before slicing. Dust with cocoa powder and heat a knife by dunking in hot water. Slice into bars and tuck in.