In a small bowl, mix 2 tablespoons of the milk with the cornstarch to make a slurry. In a separate large bowl, mash the softened cream cheese with a spoon until smooth.
In a medium saucepan, add the chopped macadamia nuts and butter, cooking and stirring over medium heat for about 5 minutes until the butter has melted and the macadamia nuts are a light golden brown. Be careful not to burn. Transfer to a separate bowl.
In the same saucepan, add the milk, coconut milk, cream, sugar, corn syrup, and salt, then bring to a rolling boil over medium-high heat, and boil for 4 minutes. Remove from the heat and whisk in the cornstarch slurry.
Return the mixture back to a boil over medium-high heat and cook, stirring constantly for 1 minute, until slightly thickened. Remove from heat and stir in the vanilla.
Slowly pour the hot milk mixture over the cream cheese, whisking until smooth, then cool completely. You can speed up the process by transfer the mixture to a gallon size Ziploc freezer bag and submerging it in an ice bath, adding more ice as needed, until cold. This only takes about 30 minutes. If chilling the mixture in the fridge though, plan on at least 4-6 hours or overnight.
Pour the ice cream base into your ice cream maker and churn until thick, about 20-30 minutes. Add the chopped macadamia nuts right at the end, then transfer to an airtight container. Freeze for at least 4 hours until the ice cream is firm.