Dissolve the cornstarch in 50ml whole milk, leave to rest.
In a small saucepan over medium heat combine the leftover whole milk, heavy cream, sugar, salt and cook until almost boiling. Add the cornstarch milk and cook constantly stirring until thickened. Take off heat, add the cream cheese, stir until smooth. Add the Baileys and the brandy, mix until thorough and smooth. Cool to room temperature, then transfer into the fridge overnight.
Freeze in your ice cream maker according to the manufacturer's instructions adding the Maltesers at the last couple of minutes of churning. Store in an airtight container or spoon right away.