Bring milk and coffee to a simmer in a saucepan. Strain through a coffee filter or clean tea towel.

Melt 500 grams of chocolate and place in a large bowl. Bring coffee-infused milk, cream, butter and glucose to the boil and pour over chocolate. Add rum and stir with a whisk until smooth and shiny.

Pour into a container and set in the fridge. Use a teaspoon to shape into five-cent-sized balls and place on a tray. Freeze.

Melt remaining chocolate. Cover a tray with the cocoa. Using your fingers, coat truffles with chocolate and drop onto cocoa so that they don't touch each other. Agitate tray so that truffles roll around and become covered in cocoa. Store in an airtight container with excess cocoa on top in the fridge.