In a medium saucepan, whisk together 1 cup of milk, sugar, cocoa powder, and salt. Whisk in remaining milk until fully combined. Heat mixture over medium heat, stirring constantly, until sugar is dissolved and very hot, but not boiling.
Whisk in pumpkin puree and pumpkin pie spice. Continue to whisk and heat mixture. Turn off and move from heat just before mixture begins to boil (do not let it boil). Immediately whisk in Kahlúa. Pour into glasses and top with whipped cream. Serve.