01 - Place chopped white chocolate in a heatproof mixing bowl.
02 - In a small saucepan, warm heavy cream and butter over medium heat just until simmering. Immediately pour over the white chocolate and let stand for 2 minutes.
03 - Gently stir the mixture with a rubber spatula until smooth and glossy.
04 - Add vanilla extract and a pinch of salt, mixing thoroughly until fully blended.
05 - Divide the mixture evenly among three bowls. Tint one part red and fold in crushed freeze-dried raspberries. Tint another part blue and fold in crushed freeze-dried blueberries. Leave the third portion plain for white.
06 - Transfer all three mixtures to the refrigerator for about 45 minutes until sufficiently firm for scooping.
07 - Using a truffle scoop or teaspoon, take about 1/2 teaspoon from each colored mixture. Press together and gently roll in your palms to create a three-tone ball. Repeat until all mixtures are used.
08 - Roll each truffle in white nonpareil sprinkles or sanding sugar for a festive finish.
09 - Place truffles on a parchment-lined baking sheet and refrigerate for 20 minutes to fully set before serving.