Lightly grease a small deep baking tin (7x11in) with a little vegetable oil. Line with greaseproof paper and grease the paper.
Sift the ingredients for the coating together into a bowl.
Squeeze the sheets to get rid of excess water and place in a small saucepan with 2 tablespoons hot water.
Meanwhile place the sugar, glucose and four tablespoons water in a saucepan and bring to the boil over medium-low heat until the caramel registers 120C (250F) in digital or jam thermometer.
While the sugar syrup is cooking, melt the gelatine over very low heat and then pour in the bowl of your stand mixer. Whisk for two minutes on medium speed.
Once the sugar reaches the right temperature, pour very carefully down the side of the bowl while still whisking.
Continue whisking at maximum speed for several minutes until the marshmallow mixture increases in volume and is glossy and thick. Add the vanilla paste and mix it in.
Stir the caramel and grated chocolate into the marshmallow mixture with an oiled silicone spatula, rippling it through gently. Pour the marshmallow mixture into the prepared tin and level (it will be very sticky). Lightly dust the surface with the coating and leave to set for 6 hours or overnight.
Cut the marshmallows into strips and then cubes (a pizza wheel is good for this purpose).
Toss in the coating to cover otherwise they will dry out. Store in an airtight container for a week.