01 - Place white chocolate in a heatproof mixing bowl.
02 - In a small saucepan, heat heavy cream and butter over medium heat just until simmering.
03 - Pour hot cream mixture over the chopped white chocolate and let stand for 2 minutes. Stir gently until completely smooth and glossy.
04 - Stir in vanilla extract and a pinch of salt until fully incorporated.
05 - Divide the chocolate mixture evenly among three bowls. Color one portion with red gel and fold in crushed freeze-dried raspberries; color another with blue gel and fold in crushed freeze-dried blueberries; leave the third portion uncolored for the white layer.
06 - Cover and refrigerate all three mixtures for 45 minutes, or until the filling is firm enough to scoop.
07 - Using a truffle scoop or teaspoon, take approximately 1/2 teaspoon from each colored portion, press together, and gently roll between your palms to create a tricolor sphere. Repeat with remaining mixture.
08 - Roll each truffle in white nonpareil sprinkles or sanding sugar for a festive finish.
09 - Refrigerate the truffles on a parchment-lined baking sheet for 20 minutes to set before serving.