In a medium saucepan off the stove, whisk egg yolks, malted milk powder, and sugar into a paste. When thoroughly combined, whisk in half and half, slowly to clear out any lumps. Put to low heat and stir frequently until custard thickens but does not yet simmer. Custard should coat the back of a spoon and a swiped finger should leave a clean line.
Strain custard into a large bowl containing chopped chocolate. Let sit undisturbed for one minute, then stir until chocolate melts completely. Add vanilla, nutmeg, and salt to taste. Transfer to an airtight container and chill overnight.
The next day, churn according to manufacturer’s instructions. During last minute of churning, add in frozen malted milk balls. Return to airtight container to freeze for at least two hours before serving.