01 - Place white chocolate in a heatproof mixing bowl.
02 - In a small saucepan, gently heat heavy cream and butter over medium heat until just simmering.
03 - Pour the hot cream and butter over the chopped white chocolate. Let stand for 2 minutes, then stir until the mixture is smooth and glossy.
04 - Stir in vanilla extract and a pinch of salt until fully incorporated.
05 - Portion the chocolate mixture evenly into three separate bowls. Color one bowl with red gel food coloring and fold in the crushed freeze-dried raspberries; color another bowl with blue gel food coloring and fold in the crushed freeze-dried blueberries; leave the third bowl plain for the white layer.
06 - Refrigerate all three bowls for 45 minutes or until mixtures are firm enough to scoop.
07 - Using a small scoop or teaspoon, collect about 1/2 teaspoon from each colored mixture. Press the portions together and gently roll between your palms to form a tricolor ball. Continue with remaining mixtures.
08 - Roll each formed truffle in white sprinkles or sanding sugar for a festive finish.
09 - Place truffles on a parchment-lined baking sheet and refrigerate for 20 minutes until set before serving.