Set out 6 (6-8 oz.) ramekins.
In a small bowl, add 1/2 cup cream. Sprinkle gelatin over cream; let sit for 5 minutes.
In a medium sauce, add 2 cups cream, sugar, salt, and gelatin-cream mixture. Cook, whisking often, over medium heat, about 6-8 minutes or until sugar and gelatin are completely dissolved. (Do not allow to boil.) Remove from heat. In a small bowl, stir together pumpkin, mascarpone, and pumpkin spice. Add to cream mixture. Return to heat; stir until completely dissolved.
Ladle pumpkin mixture into the ramekins up to about 2/3 full, dividing equally among ramekins. Refrigerate 4 hours or until set.
Before serving, in a small saucepan over medium heat, add chocolate hazelnut, remaining 1/3 cup cream, and orange zest. Cook, stirring, until chocolate has completely melted and is smooth.
To serve, run a small knife around edge of the panna cotta. Invert each onto a dessert plate. For each serving, place panna cotta on plate; drizzle with chocolate hazelnut ganache. Top each hazelnuts and grated semi-sweet chocolate.