In a bowl, stir together 1⁄4 cup milk and the cornstarch; set aside
In a medium saucepan, whisk together remaining milk, heavy cream, sugar, syrup, and salt and bring to a boil over medium-high heat.
Cook for 5 minutes, watch it carefully as it will boil over quickly!
Stir in the cornstarch mix and then return to a boil and cook. Stir constantly until thickened, about 3 minutes.
Place the softened cream cheese in a bowl and pour in 1⁄4 cup hot milk mixture.
Whisk until completely smooth. No lumps in the cream cheese.
Add it back into the main mixture and stir all together. Add in the vanilla
Put the mixture, covered in the refrigerator. It must be completely cooled so leave it for a few hours or overnight.
Pour mixture into an ice cream maker; process according to manufacturer's instructions.
When the ice cream is thickened, add in the marshmallows fluff and 4 cups of Lucky Charm marshmallows and churn a few times until incorporated. Do not over mix.
Pour into a container to freeze.