Chop 8 ounces of white chocolate into small, uniform pieces and place in a medium heatproof bowl. Set aside at room temperature.

Heat the heavy cream in a small saucepan over medium heat until it just begins to steam and small bubbles form around the edges, about 3-4 minutes. Do not let it boil.

Pour the hot cream over the chopped white chocolate and let it sit undisturbed for 2 minutes to soften the chocolate. Then whisk gently from the center outward until completely smooth and glossy.

Add the softened butter, lemon juice, lemon zest, vanilla extract, and salt to the ganache. Whisk until the butter is fully incorporated and the mixture is silky. The lemon juice may cause slight graininess at first, but keep whisking until smooth.

Cover the bowl with plastic wrap, pressing it directly onto the surface of the ganache to prevent a skin from forming. Refrigerate for 2-3 hours until firm enough to scoop but not rock-hard.

Line a baking sheet with parchment paper. Use a small cookie scoop or teaspoon to portion the ganache into 1-inch balls, then roll each between your palms to smooth. Place on the prepared sheet and refrigerate for 30 minutes.

Melt the remaining 4 ounces of white chocolate in a microwave-safe bowl in 20-second intervals, stirring between each, until smooth. Let it cool for 3-4 minutes until slightly thickened but still fluid.

Working one at a time, drop a truffle into the melted chocolate, use a fork to roll it and coat completely, then lift it out and tap the fork gently on the bowl edge to remove excess chocolate. Slide onto parchment paper.

If using toppings, sprinkle them on immediately while the coating is wet. Let the truffles set at room temperature for 20 minutes, or refrigerate for 10 minutes until the coating is firm and no longer glossy.