Preheat the oven to 130C. Spread the chopped white chocolate on a baking pan lined with parchment paper, add the cocoa butter, mix it with the chocolate chunks and bake the mixture for 10min, then take out, stir with a spatula to reveal a slightly more caramelized layer of chocolate underneath. Return into the oven and bake another 10min, then remove and stir again. Continue thus caramelising the chocolate until it turns a lovely golden brown color reminiscent of dulce de leche.
Combine the cornstarch and 50ml whole milk, leave to rest.
In a small saucepan combine the leftover milk, heavy cream, sugar and a pinch of salt, place on medium heat, cook until almost boiling, add the hot liquid caramelized chocolate (reheat it on a Bain-Marie if necessary), stir until combined, then add the cornstarch milk and cook on medium constantly stirring until thickened. Remove from heat, add the cream cheese, mix until smooth and combined. Cool to room temperature, then transfer to the fridge overnight.
Churn in your ice cream maker according to the manufacturer's instructions, store in an airtight container in the freezer or spoon right away.