01 - Place the white chocolate in a heatproof mixing bowl.
02 - Warm heavy cream and unsalted butter in a small saucepan over medium heat until just simmering.
03 - Pour the heated cream and butter mixture over the white chocolate. Allow to sit for 2 minutes, then stir with a rubber spatula until smooth and glossy.
04 - Incorporate vanilla extract and a pinch of salt into the melted chocolate mixture, stirring until fully combined.
05 - Divide the base into three bowls. Tint one portion with red gel food coloring and fold in crushed freeze-dried raspberries. Tint a second bowl with blue gel food coloring and fold in crushed freeze-dried blueberries. Leave the third bowl plain for the white layer.
06 - Refrigerate the tinted and plain mixtures for 45 minutes, or until the texture is firm enough to scoop.
07 - Scoop approximately 1/2 teaspoon from each colored mixture. Press together and gently roll between your palms to form a single tricolor ball. Repeat until all mixtures are used.
08 - Roll each truffle in white sprinkles or sanding sugar. Place on a parchment-lined baking sheet and refrigerate for 20 minutes to set before serving.