01 - Combine raspberries, sugar, and lemon juice in a small saucepan. Cook over medium heat, stirring constantly, until raspberries break down completely and mixture thickens, approximately 5 to 7 minutes. Press through a fine-mesh sieve to remove seeds. Allow to cool completely before proceeding.
02 - Place 10.5 ounces white chocolate, heavy cream, and butter in a heatproof bowl. Set over a pot of simmering water, creating a double boiler. Stir continuously until completely melted and smooth. Remove from heat, then stir in vanilla extract and 2 tablespoons of the cooled raspberry reduction. Reserve remaining sauce for another use.
03 - Cover the ganache mixture and refrigerate for 1 to 2 hours, or until firm enough to scoop cleanly and hold its shape when rolled.
04 - Line a baking sheet with parchment paper. Scoop 1-tablespoon portions of the chilled ganache and roll between palms to form smooth balls. Arrange on prepared baking sheet and freeze for 30 minutes to firm.
05 - Melt 5.25 ounces white chocolate for coating. Using a fork, dip each chilled truffle into melted chocolate, ensuring complete coverage. Allow excess chocolate to drip off before returning to parchment paper. Immediately sprinkle tops with crushed freeze-dried raspberries if desired.
06 - Refrigerate dipped truffles until chocolate coating is completely set, approximately 20 minutes. Store in an airtight container in the refrigerator until ready to serve.