In a large bowl, beat softened butter and powdered sugar together until smooth.
Mix in salt, orange extract, and orange zest until well combined.
Stir in melted white chocolate until fully incorporated.
Gradually add powdered milk and mix until a soft dough forms.
Chill the dough in the fridge for at least 1 hour to firm up.
Scoop out tablespoon-sized portions and roll into balls.
Roll each truffle in white sanding sugar for a sparkly finish.
Store in an airtight container in the fridge until ready to serve.