1. Place the gelatin sheets in an empty bowl.
2. Fill the bowl with water to cover the gelatin sheets. Leave them to soak.
3. In the meantime, place 4.22 oz. of water in a pan and bring to a boil. Add the granulated sugar and heat to 220°F. When it reaches that temperature (check with a cooking thermometer), remove from the heat.
4. Add the couverture chocolate and whisk until the mixture takes on an even consistency, then follow this up by adding the cocoa powder. Carry on whisking until everything is nice and even.
5. Next, add the heavy cream to the mixture and whisk.
6. Leave the mixture to cool down to 140°F, and then add the water-soaked gelatin sheets. Ensure that you remove any excess water on the sheets before placing in the mixture.
7. Pour the mixture through a sieve into a jug.
8. Use a hand blender to stir the mixture so that the gelatin blends in as smoothly as possible.
9. Leave the mixture to cool to 85°F.
10. Once the mixture has cooled, take your chilled cake and place it on an inverted cake tray. Ideally the cake tray should be of smaller dimensions than the actual cake. Pour the glazing mixture onto it evenly, and use a spatula to ensure you cover the exposed underside.
11. Allow a few hours for the glazing to set on the cake.
12. Decorate as desired.