To a cocktail shaker or jar with a tight-fitting lid, combine the brown sugar syrup, pumpkin pie spice, espresso, and a big handful of ice cubes.
Shake vigorously for 15–20 seconds until the mixture is frothy and well-chilled.
Pour the entire shaken espresso mixture into a tall glass, ice included.
Top with oat milk, leaving room for cold foam, and set aside.
In a small cup, make the cold foam by combining the pumpkin spice syrup, oat milk, and heavy cream.
Froth with a handheld milk frother for 15–30 seconds until thick and creamy.
Pour the cold foam over the espresso mixture.
Sprinkle with extra pumpkin pie spice and enjoy!