First, brew your coffee. Start with 2 cups of hot strong coffee or 2 shots of espresso so everything stays piping hot when the base is ready.
In a small saucepan, whisk together the milk, pumpkin puree, brown sugar, and pumpkin pie spice. Turn the heat to medium and watch the cinnamon and nutmeg swirl into ribbons of color as the kitchen starts smelling like October.
Heat gently for 4 to 5 minutes, whisking constantly, until the mixture is steaming and slightly thickened. Do not let it reach a rolling boil. If it bubbles aggressively, lower the heat so the milk stays smooth.
Remove the pan from the heat and stir in the vanilla extract. Taste it now and adjust the sweetness or spice before assembly.
Make the sweet cream by adding the heavy cream and powdered sugar to a jar with a tight lid. Shake for 45 to 60 seconds until the cream doubles in volume and holds its shape on a spoon.
Divide the hot coffee between two large mugs, filling each about three-quarters full.
Pour the pumpkin base over the coffee, using a spoon to hold back any foam. Stir gently so the coffee and pumpkin base swirl together without becoming completely uniform.
Spoon the sweet cream over the back of a spoon onto each mug so it floats. Dust with a pinch of cinnamon or pumpkin pie spice and serve immediately while steaming.