Chop the dark chocolate into small, uniform pieces and place in a medium bowl—smaller pieces ensure even, quick melting. Heat the heavy cream in a small saucepan over medium heat, stirring occasionally, until it just begins to simmer (small bubbles will form around the edges). This takes about 3-4 minutes. Immediately pour the hot cream over the chopped chocolate and let it sit undisturbed for 2-3 minutes—the residual heat will gently melt the chocolate without scorching it.

Stir the chocolate and cream mixture gently but thoroughly with a rubber spatula or wooden spoon until completely smooth and glossy, about 1-2 minutes. Add the butter and vanilla extract, stirring until fully incorporated. I find that using quality butter like Kerrygold makes a noticeable difference in the richness and mouthfeel of the final truffle. The ganache should look like thick, luxurious chocolate sauce at this point.

Pour the ganache into a shallow bowl or small baking dish and refrigerate for at least 2 hours, until it's firm enough to scoop but still slightly soft. You want it to hold its shape when rolled, not be rock-hard. A helpful tip: if your ganache becomes too firm to work with, let it sit at room temperature for 5-10 minutes to soften slightly—this makes rolling much easier and prevents cracking.

Scoop small portions of chilled ganache using a small cookie scoop, melon baller, or two teaspoons, then quickly roll each piece between your palms into a smooth ball. Work quickly so the ganache doesn't warm too much. Dust each finished truffle generously with unsweetened cocoa powder by rolling it in a shallow dish or shaking it in a container. Store in an airtight container in the refrigerator for up to 2 weeks, or freeze for longer storage.