Finely chop the chocolate and place it in a heatproof bowl.
Combine cream and instant espresso (if you choose to use it) in a small saucepan over medium heat just until it just comes to a simmer. Small bubbles will begin to form around the edges of the pan.
Remove from heat and immediately pour it over chopped chocolate. Cover the bowl and let stand without stirring for 2 minutes.
Gently stir mixture in a circular motion using a rubber spatula, starting from the center and working your way out to the sides, until it transforms into a smooth and glossy mixture. Let the ganache cool at room temperature for about 30 minutes, and then cover and refrigerate for 2 hours or until firm.
Scoop up heaped teaspoons of ganache, roll them into smooth balls between the palms of your hands and then roll them around in cocoa powder or sprinkles to coat them evenly. Store in the fridge but serve at room temperature.