In a large bowl using a whisk, or in a large bowl of an electric mixer using the whisk attachment, or using a hand held mixer...beat your heavy cream until stiff peaks form.
In another large bowl, whisk together the sweetened condensed milk and the vanilla.
Fold the sweetened condensed vanilla mixture into the heavy whipping cream. Cover the bowl with plastic wrap and place in the freezer while you make the cinnamon swirl.
In a small saucepan set over medium low heat, whisk together the dark brown sugar, the water and the cinnamon until the sugar dissolves and the mixture is syrupy. About 5 minutes.
Remove the pan from the heat and whisk in the butter or vegan baking stick until it has all melted.
When it has melted, vigorously whisk in the light corn syrup until it is fully combined.
Take your bowl of vanilla ice cream out of the freezer.
Carefully pour the cinnamon mixture into the ice cream in a swirl like motion.
The hot cinnamon mixture will start to get stringy as it hits the cold ice cream. This is normal.
Fold it in using a spatula and pour the ice cream into a freezer safe container. If you’re using a 9x5 loaf pan, make sure you cover it with plastic wrap and the aluminum foil to prevent ice crystals.
Pop in the freezer and allow to freeze overnight before serving. Enjoy!