Whisk together the sugar, soy milk powder, and sea salt in a small bowl. Set aside.
Use a serrated knife to cut the cocoa butter into smaller bits. The smaller the bits, the quicker it will melt. Transfer the chopped cocoa butter into a microwave-safe bowl. Heat the cocoa butter for 1 minute. Leave the bowl in the microwave. Place a plate over the top of the bowl and let it sit in the microwave until all the cocoa butter bits have melted. This allows the bowl to cool too.
When the cocoa butter is fully melted and the bowl is cool enough to handle. remove it from the microwave. Whisk in the powdered sugar mixture, stirring until it's all combined. Add the vanilla extract and lecithin. Continue whisking.
Return the bowl to the microwave and heat for another 30 seconds. Use oven mitts to remove the bowl from the microwave. Whisk the contents one last time. Let the bowl cool for a minute. Then pour the melted white chocolate into your candy mold.
Transfer the mold to the fridge to allow the chocolate to set. It should be chilled at least 30 minutes.
You can substitute coconut milk powder for soy milk powder.Soy lecithin is an emulsifier that helps stabilize the fat from cocoa butter, sugar, and soy milk. Without it, the chocolate is oily.