In a small saucepan over medium heat, combine the milk, chocolate, chile pepper, cinnamon, brown sugar, vanilla, salt, peppercorns, allspice and cayenne. Simmer, whisking until the chocolate has melted, about 5 minutes. Remove from the heat and allow to infuse for 15 minutes, then return to medium heat and warm until hot.
Strain through a fine mesh strainer and add the Grand Marnier. Top with whipped cream and a dusting of chile powder and serve.