Begin by defrosting the frozen raspberries.
Finely chop the white chocolate and set it aside. (This step is crucial to ensure the chocolate melts evenly in the raspberry puree.)
Add the thawed raspberries to a blender and blend until smooth.
Strain the raspberry puree through a fine mesh strainer to remove the seeds. If the puree is too thick, add a small amount of water to achieve a smoother texture (but maintain a thick puree consistency).
In a saucepan over medium heat, combine the raspberry puree and powdered sugar. Stir frequently and bring to a boil.
Once boiling, reduce the heat to low and simmer, stirring often, until the mixture reduces by about half. This process takes approximately 25 minutes.
Add the heavy whipping cream to the reduced raspberry mixture and stir until fully incorporated.
In a large bowl, add the chopped white chocolate. Pour the warm raspberry mixture over the chocolate and stir until the chocolate is fully melted and the mixture is smooth. (You can place the bowl over a warm water bath to help melt the chocolate, if needed.)
Cover the bowl with plastic wrap and refrigerate the ganache for at least 2 hours until firm.
Once the ganache is firm, scoop small amounts (about 1 inch in diameter) and roll them into balls using your hands.
Melt the dark chocolate in a microwave or over a double boiler.
Using a fork, dip each truffle into the melted dark chocolate, letting any excess drip off before placing the truffle on a parchment-lined baking sheet.
Repeat the process for all the truffles.
Refrigerate the truffles for about 25 minutes until the chocolate coating is fully set.
Optional: Melt pink chocolate or candy melts and drizzle over the truffles for decoration.