Chop the chocolate into small pieces and place them in a heatproof bowl.
Warm the heavy cream in a small saucepan over low heat until it just begins to steam—avoid boiling.
Pour the hot cream over the chopped chocolate and let sit for 2-3 minutes, allowing the chocolate to soften and meld.
Gently stir the mixture with a spatula until smooth, glossy, and completely combined—this creates a rich ganache.
Add the butter and vanilla extract to the ganache and stir until fully incorporated, resulting in a thick, fudgy texture.
Cover the bowl with plastic wrap and refrigerate for 1-2 hours until the ganache is firm enough to scoop and shape.
Using a teaspoon or small scoop, portion out the chilled ganache and quickly roll between your palms into 1-inch balls, placing each on parchment paper.
Sift the cocoa powder onto a plate and roll each truffle in the cocoa, coating evenly for a beautiful, velvety finish.
Return the coated truffles to the parchment-lined tray and refrigerate for an additional 30 minutes to set the coating.
Serve the truffles straight from the fridge for a firm, fudgy bite, or allow them to sit at room temperature for 5 minutes for a softer, more aromatic experience.