Finely chop the dark chocolate and place it in a heatproof bowl. The smaller the pieces, the easier they will melt.

In a small saucepan, warm the heavy cream over medium-low heat until it is hot but not boiling. The cream should begin to simmer slightly around the edges. Remove from heat immediately to prevent scorching.

Pour the heated cream over the chopped chocolate. Allow the mixture to sit undisturbed for 3 minutes, then gently stir until smooth and glossy. If any pieces of chocolate remain unmelted, briefly microwave the mixture in 10-second intervals, stirring between each, until fully incorporated.

Let the ganache sit at room temperature for 1 hour before covering and refrigerating for at least 2 hours or overnight. The mixture should be firm enough to scoop into small portions.

Using a small cookie scoop or a spoon, portion out 1 tablespoon-sized scoops of ganache and place them on a parchment-lined tray. If the ganache is too soft, freeze for 10 minutes to firm up. Roll each portion between the palms of your hands to create smooth, round truffles.

Place the cocoa powder in a shallow bowl. Roll each truffle in the cocoa powder until fully coated. This gives the truffles a classic appearance and prevents them from sticking.

Transfer the truffles to an airtight container and refrigerate until ready to serve. Enjoy chilled or at room temperature for a softer texture.