Whisk together brown sugar, cocoa powder, cornstarch, cinnamon, and salt in a heavy medium saucepan.

Whisk in almond milk until well combined.

Bring the mixture to a boil over medium heat, whisking often to prevent scorching.

Once boiling, continue to whisk for 1 minute to thicken the pudding.

Remove the saucepan from the heat.

Whisk in the butter until it is fully melted and incorporated into the pudding.

Stir in the vanilla extract.

Pour the pudding into a bowl.

Cover the surface of the pudding with a piece of buttered wax paper to prevent a skin from forming.

Chill in the refrigerator for at least 1 1/2 hours, or until fully cold and set.