Place the chocolate into a large microwave-safe bowl, and heat in 30 second intervals, stirring after each one, until melted and smooth.
Stir in the vanilla and malt powder until combined, then stir in the condensed milk until almost combined. Fold in the Maltesers.
Spread the mixture into the prepared pan, and smooth out the top. Top with extra Maltesers, if desired. Refrigerate for 2 - 4 hours or overnight until completely set.
Fudge can be stored, in an airtight container at room temperature for 1 week, or in the fridge for 2 - 3 weeks. It also freezes well for up to 2 months. Thaw overnight in the fridge before serving.
The calories are an estimate only.