Begin by finely chopping dark chocolate and placing it in a heatproof bowl. Heat heavy cream in a saucepan until steaming but not boiling, then pour it over the chocolate. Stir gently until melted and smooth.

Add instant coffee to the melted chocolate and cream mixture. Stir well to ensure the coffee is fully dissolved and incorporated.

Cover the bowl and place it in the refrigerator. Allow the mixture to chill for about 2 hours until it firms up.

Use a small cookie scoop or spoon to portion out the mixture. Roll each into smooth balls, about 1 inch in diameter.

Melt milk chocolate in a heatproof bowl, then dip each ball in the melted chocolate or roll them in cocoa powder.

Allow the coated truffles to set at room temperature for about 30 minutes, or refrigerate until fully firm.