Place the finely chopped white chocolate into a dry, heatproof glass or stainless steel mixing bowl.

In a small heavy-bottomed saucepan, heat the heavy cream over medium-high heat until it reaches a simmer (approximately 80°C / 176°F).

Pour the hot cream immediately over the white chocolate; allow the mixture to sit undisturbed for 5 minutes to facilitate even melting.

Using a silicone spatula, stir the mixture in small concentric circles from the center outward until a smooth, homogenous ganache forms.

Add the softened butter, lemon zest, lemon juice, and vanilla extract to the ganache; whisk gently until fully incorporated.

Press a layer of plastic wrap directly onto the surface of the ganache to prevent oxidation and skin formation; refrigerate for a minimum of 2 hours or until the mass is firm enough to handle.

Using a small mechanical scoop or teaspoon, portion the chilled ganache into 15g units (approximately 1 tablespoon).

Roll each portion between chilled palms to form a sphere, then immediately roll in confectioners' sugar until thoroughly coated.

Store the finished truffles in an airtight container in the refrigerator.