Dissolve 3tsp cornstarch in 50ml whole milk, leave to rest.
In a small saucepan over medium high heat combine the heavy cream, the leftover milk, sugar, pinch salt, cocoa powder, malted milk powder (think Horlicks Original) and the chopped milk chocolate, cook stirring until fully dissolved, bring to an almost boil, add the cornstarch milk and cook on medium stirring constantly until thickened. Take off heat, add the cream cheese, mix well until smooth and silky. Cool to room temperature, then transfer into the fridge overnight.
Freeze in your ice cream maker according to the manufacturer's instructions adding the halved #maltesers at the last couple of minutes of churning. Store in an airtight container or spoon right away.