Arrange the oven racks in the centre and lower third of the oven. Place a baking dish or roasting pan on the bottom rack and fill halfway with water. Preheat the oven to 162°C.
Coat a 9-inch springform pan with nonstick cooking spray. Place 2 tablespoons of the sugar and the cookies in the bowl of a food processor and pulse until they become fine crumbs. Add the melted butter and pulse until moist. Press the mixture into the bottom and slightly up the sides of the springform pan. Set aside.
Beat the cream cheese and remaining 300g cups sugar until creamy in the bowl of a standing mixer or using a hand mixer. Beat in the eggs 1 at a time until just incorporated. Beat in the sour cream, flour and vanilla. Reserve 720ml of the thick batter (this does not need to be refrigerated) and stir the melted chocolate and almond extract into the remaining batter. (Don't worry if there are tiny flecks of chocolate in the batter, they will bake into the cheesecake.) Pour the chocolate batter over the crust. Bake the cheesecake on the centre rack of the oven until the edges are just set but the centre is still a bit wobbly, 30 to 35 minutes.
Slowly pour the reserved vanilla batter over the chocolate layer and continue to bake until the cheesecake is just set but the centre is slightly jiggly, another 40 to 45 minutes. Turn off the oven, open the door slightly and let the cheesecake cool 20 minutes. Remove and run a knife around the edge of the pan. Cool to room temperature and then chill overnight.
Before serving, let stand at room temperature for about 1 hour. Remove the sides of the pan. Garnish generously with white and milk chocolate curls.