Preheat the oven to 375°F (190°C).
Roll out the pie crust and fit it into a 9-inch pie pan. Trim and crimp the edges as desired.
Blind bake the crust by lining it with parchment paper and filling it with pie weights. Bake for 10 minutes, then remove the weights and bake for another 5 minutes. Let cool.
In a saucepan over medium heat, combine heavy cream and milk. Heat until steaming but not boiling.
Remove from heat and add chopped dark chocolate. Stir until smooth.
Whisk in the sugar, cinnamon, cayenne, vanilla extract, and salt.
In a mixing bowl, lightly beat the eggs. Slowly whisk in a small amount of the warm chocolate mixture to temper the eggs.
Gradually add the tempered eggs back into the saucepan, stirring constantly.
Pour the chocolate filling into the pre-baked pie crust.
Bake for 20-25 minutes, or until the filling is set but slightly wobbly in the center.
Let the pie cool at room temperature for at least 2 hours before serving.