Whisk the yolks and ¼ cup of the brown sugar until creamy. Set aside. Heat the cream, milk, remaining ½ cup of sugar, and salt in a medium pot and cook on medium heat for 2-3 minutes, until the sugar is dissolved and the milk is nearly simmering. Lower the heat and scoop a ½ cup of the milk mixture into the creamed yolks, whisking the entire time to combine. Scoop another ½ cup of milk into the yolks, whisking the entire time to combine.
Pour the heated yolk mixture back into the pot, again whisking the entire time to combine. Then, using a spatula, slowly stir the custard mixture while it heats. The custard should thicken in 3-5 minutes. You will know it’s ready when it coats the back of a spoon and holds its shape when you draw your finger through it.
Quickly remove from heat and stir in cream cheese and lemon zest. Should your cream cheese curdle, simply pour the mixture through a fine sieve to remove lumps.
Pulse the blueberries in a blender until liquid. Stir into ice cream mixture.
Pour mixture into a thick ziplock bag and chill in the fridge for at least 4 hours, and up to overnight.
Once chilled, pour ice cream into your ice cream maker and churn according to manufacturer’s instructions. Transfer to freezer-proof container and allow to harden for at least 6 hours. Then serve!