Bring the gelato out about 15 minutes before you’re ready to use it so it can soften slightly.
Turn the pandoro upside down. Using a knife, cut a circle in the middle, leaving about a 2cm border. Pull this piece out in one piece — this will be your plug. Carefully cut down into the pandoro, keeping that 2cm border intact, then scoop out the centre. Remember the pandoro tapers in and is star-shaped, so it will be thinner in some spots and thicker in others, especially towards the base. Reserve the scooped-out pandoro for another use (my favourite is frying it in butter), but keep the round plug.
Spoon the different gelato flavours into the hollow, using the back of a spoon to gently push them down. Keep layering in a loose, random way to create a marbled, mottled effect when you slice it, pressing down as you go.
Place the reserved plug back on top. Cover with a piece of baking paper, then wrap the whole pandoro tightly in plastic (or slip it back into the bag it came in). Freeze overnight, or for up to 5 days.
To serve, place on a plate and dust generously with icing sugar. Serve immediately.
You can buy Pandoro at many supermarkets now or Italian Deli's
Remember this is an ice cream dessert, so it will melt if left out.