• Place the chocolate in the fridge 30 minutes before making the mix. Break the chocolate into smaller pieces and transfer it in a food processor. Being cold ensures that the chocolate doesn't melt during processing. Pulse until the chocolate is finely ground.
• Add the remaining ingredients and pulse 2-3 times until well combined.
• If you don't have a food processor, grate the chocolate on a fine grater then sift the cocoa, cornstarch, powdered milk, sugar and salt in a bowl and stir in the grated chocolate.
• Store the hot chocolate mix in an airtight container or in a sealed glass jar.

To prepare the hot chocolate:

• Bring 1 cup of milk to a boil in a small saucepan.
• Stir in 1 1/2 - 2 tablespoons of hot chocolate mix and stir well with a whisk for 1-2 minutes over low heat until it thickens.
• Pour into a mug and serve hot.