Special equipment: a candy thermometer
Grease a 9-by-13-inch pan lightly with cooking spray and then line it with parchment so that the paper hangs over all the sides (this will allow you to remove the fudge from the pan).
Combine the sugar, butter, cream, vanilla and salt in a large saucepot over high heat. Bring to a boil and then cook until the mixture reaches 240 degrees F on a candy thermometer, about 4 minutes.
Meanwhile, in the bowl of a stand mixer fitted with the paddle attachment, mix the milk chocolate and white chocolate chips, marshmallow cream and malted milk powder. With the speed set to low, slowly pour in the boiling sugar mixture and paddle until well combined.
Pour the fudge into the prepared pan; tap the pan to even out the fudge. Evenly sprinkle the broken malted milk balls over the top of the fudge and lightly press them down into the fudge.
Chill the fudge until completely cooled, about 3 hours. Remove the fudge from the pan and cut it into squares.
Serve with vanilla ice cream. Store any remaining fudge in an airtight container.