01 - Place finely chopped white chocolate in a heatproof mixing bowl.
02 - In a small saucepan, heat the heavy cream and unsalted butter over medium heat until just simmering. Pour mixture over the white chocolate and let sit for 2 minutes.
03 - Stir the mixture until smooth and glossy. Add vanilla extract and a pinch of salt, mixing until fully integrated.
04 - Divide truffle base evenly into three separate bowls. Tint one portion with red gel coloring and fold in crushed freeze-dried raspberries; tint another portion with blue gel coloring and fold in crushed freeze-dried blueberries; leave the remaining portion plain for the white layer.
05 - Refrigerate all three bowls for 45 minutes or until mixtures are firm and scoopable.
06 - Using a small scoop or teaspoon, take 1/2 teaspoon of each color and press together. Gently roll the portions between your palms to form one tricolor ball. Repeat with remaining mixture.
07 - Roll each truffle in white nonpareil sprinkles or sanding sugar for a festive appearance.
08 - Place truffles on a parchment-lined baking sheet and chill in the refrigerator for 20 minutes before serving.