Preheat oven to 350°F (180°C). Mix together graham cracker crumbs, melted butter, 2 tbsp (30 mL) sugar and 1/4 tsp (1 mL) salt. Press mixture firmly into bottom of 9-in. (23-cm) springform pan. Bake crust 10 to 12 min. until deeply golden. Cool completely. Reduce oven to 325°F (160°F). Bring kettle of water to boil.
Set springform pan on piece of heavy-duty foil large enough to wrap bottom and sides of pan (this is to prevent water bath from seeping into springform pan during baking). Place it inside roasting pan. In large bowl, using electric mixer, beat cream cheese, remaining 3/4 cup (175 mL) sugar and remaining 1/4 tsp (1 mL) salt until smooth and fluffy. Beat in melted white chocolate, eggs one at a time, orange zest, orange juice and vanilla. Pour batter onto crust in springform pan.
Place roasting pan (with springform inside) into oven; pour in enough boiled water into roasting pan to come half-way up outside of springform pan. Bake 50 min. to 1 hr. until batter is set but jiggles slightly in the centre. Turn off heat and let cheesecake cool in oven, with door ajar, for about 1 hr. (gradual heat decline helps prevent cheesecake from cracking). Remove springform pan from water bath. Run thin knife around cheesecake to release from pan. Cool cheesecake (still in springform pan) completely. chill 6 hr. overnight or up to 2 days.
To decorate, spoon melted and cooled dark chocolate into piping bag fitted with very small round tip or re-sealable bag with small corner snipped off. Using freehand, pipe lacy patterns/squiggles onto parchment paper-lined baking sheet (make patches of "chocolate lace" roughly 2-in./5-cm square). Chill 10 min. until chocolate hardens. Remove from parchment by gently peeling or lifting off with offset spatula. Remove ring of spring-form pan. Gently press pieces of "chocolate lace" onto sides and top surface of cheesecake for decoration.
Alternatively garnish with orange zest and white chocolate shavings.