For the caramel: In a medium saucepan, stir together the sugar, corn syrup and water until the sugar is completely moistened. Heat, stirring constantly, until the sugar dissolves and the syrup is bubbling. Stop stirring completely and let the syrup boil undisturbed until it turns a deep amber (380° F). Remove it immediately from the heat because the temperature will continue to rise, or remove it slightly before it reaches temperature and, as soon as it does, slowly pour in ¼ cup of hot cream. It will bubble up furiously.
Use a silicon spatula to stir mixture gently; scraping the thicker part that settles on the bottom. Return it to a very low heat, continuing to stir gently for one minute, until the mixture is uniform in color and the caramel is fully dissolved.
Remove it from the heat and gently stir in the butter until incorporated. The mixture will be a little streaky, but becomes uniform once cooked and stirred.
Pour ½ cup of the caramel into a glass measure. Store any remaining caramel for future use.
In a custard cup set in a saucepan surrounded by simmering water (stirring often), scald the remaining cream (as done before with chocolate ganache). Remove it from the heat and whisk in the cocoa. Stir in hot caramel mixture until uniform in color. Cover with plastic wrap and let it cool for 40 minutes.
For the whipped cream: Into a medium bowl, pour ¾ plus 2 tbsp of heavy cream and refrigerate for 15 minutes.
In a 1 glass measuring cup, stir together the remaining 2 tbsp of cream and the gelatin and let it soften for 3 minutes. If it will sit longer, cover with plastic wrap to prevent evaporation.
Place the cup in a pan of simmering water for a few minutes, stirring occasionally, until the gelatin is dissolved. The gelatin will thicken slightly. Remove it from the heat, cover, and let it cool for about 20 minutes until it is 85° to 90°F (if cooler, the gelatin will set and will need to be reheated). Stir in the vanilla.
In a chilled bowl, whip the cream with a handheld mixer just until traces of the beater marks begin to show. Scrape the caramel mixture and use a chilled whisk to whip the cream by hand, just until soft peaks form when the whisk is lifted, While whisking, add the gelatin mixture and continue whisking just until stiff peaks form when the whisk is lifted. Cover and refrigerate until ready to use.