Before you start making the caramel, set out two glasses, then use the oil to lightly coat a non-stick liner. Put it on a wooden chopping board.

Heat the sugar in a saucepan until it starts to melt, swirling the pan gently to make sure it melts evenly. When the sugar is a deep gold colour, remove the caramel from the heat and leave it to cool for a couple of minutes. Very carefully add the light soy sauce – the mixture may foam up, but continue stirring it until you have a smooth, thick caramel. Quickly use a mini spatula or silicone brush to spread some of the caramel down the inside of each glass in stripes, then leave to set. Pour the remaining caramel onto the non-stick liner in stripes (don’t worry if this is not exact). Leave to cool until set, then break into shards.

Snap a few caramel shards into pieces and drop them into the base of the glasses. Put the ice cream and milk in a blender. Whizz until smooth, then pour into the prepared glasses.

Top the milkshakes with the crushed Maltesers and a spoonful of whipped cream, if using. Break off pieces of the remaining caramel shards and use these to decorate the top. Serve straightaway, as the caramel will quickly start to soften and melt.