Malted-milk powder adds richness and complexity to hot chocolate.
In a medium saucepan, heat milk and vanilla over medium heat just until milk begins to steam, 5 to 6 minutes. Add chopped chocolate, and whisk until completely melted and combined.
Pour malt powder into a warmed serving pitcher or another saucepan. Add hot chocolate mixture, whisking thoroughly until powder dissolves. Divide among four mugs; serve immediately.