Grease or line a 9-inch springform pan or deep-dish pie plate. Combine the graham-cracker crumbs, melted unsalted butter, and granulated sugar, then press the mixture firmly over the bottom and slightly up the sides of the pan. Chill the crust while preparing the filling.

Whisk the orange gelatin dessert mix into the boiling water until completely dissolved. Stir in the cold water, then let the mixture cool until it is no longer warm but has not started to set.

Beat the softened cream cheese and powdered sugar until smooth and creamy. Mix in the vanilla extract and finely grated orange zest.

Slowly blend the cooled gelatin mixture into the cream cheese mixture. Add it gradually so the filling stays smooth and the gelatin does not shock the cream cheese.

Fold in the thawed whipped topping gently in two or three additions. Continue only until the filling is evenly combined and light.

Spoon the filling over the chilled graham-cracker crust and smooth the top with a spatula. Refrigerate for at least 4 hours, preferably overnight, until firm.

Before serving, decorate the cheesecake with the additional whipped topping, orange zest or thin orange slices, and white chocolate curls if desired. Run a thin knife around the edge before releasing the springform pan, then slice with a clean knife.