In a large bowl, combine graham cracker crumbs, melted butter, sugar, and cocoa powder.

Pour the mixture into the pan. Spread into an even layer, then press until the crumbs are compact. Refrigerate for at least 30 minutes. (The crust can be made ahead) Meanwhile, prepare the cheesecake.

In a small bowl, soak gelatin sheets in cold water. Set aside.

Heat 1 cup of heavy cream, sugar, and salt in a small saucepan over low heat until small bubbles appear around edges. Remove from heat. Squeeze out excess water from softened gelatin and stir it into the mixture until gelatin dissolves. Set aside and let the mixture to cool.

Blend avocados in food processor until smooth. Set aside.

In a large bowl using a hand mixer or a stand mixer with the whisk attachment, whip the remaining 1 cup heavy cream until stiff peak.

In a large bowl using a hand mixer or a stand mixer with the paddle attachment, beat blended avocados with cream cheese and cream mixture until well combined.

Add lime juice, vanilla extract, and whipped cream into the mixture and beat until well combined. 

Pour the filling into prepared crust and spread into an even layer. Use the back of spoon to sculpt the filling into swirls.

Cover with plastic wrap and refrigerate until the filling is firm for 6 hours or overnight.

Dust the top with cocoa powder. Before serving, remove the sides of the springform pan.