Preheat your oven to 350°F (175°C) and prepare a 9-inch fluted tart pan with non-stick spray.

In a food processor, combine crushed graham crackers, melted unsalted butter, and granulated sugar and mix until fine crumbs. Press into tart pan and bake for 8 minutes.

Combine cranberries, granulated sugar, cornstarch, and water in a medium saucepan. Boil, then simmer for 10 minutes until thick.

In a small saucepan, heat heavy cream and butter until bubbling. Pour hot mixture over chopped white chocolate and whisk until smooth.

Spread cooled cranberry filling over the crust, then pour white chocolate ganache on top and smooth evenly.

Cover with plastic wrap and refrigerate for several hours, preferably overnight. Garnish before serving.