Put white chocolate in a microwave-safe dish and microwave in 30-second intervals, stirring, until smooth.
In a medium bowl, whisk the flour, cocoa, baking powder and salt.
In a large bowl, whisk eggs, canola oil and food colouring. Add granulated sugar and melted white chocolate, whisking until smooth. Stir in flour mixture until well combined. Transfer dough to a piece of plastic wrap and refrigerate until firm, at least 2 hours.
Preheat oven to 300ºF. Line baking sheet with parchment paper. Put confectioner’s sugar in a small bowl.
Roll tablespoonfuls of dough into balls; toss into confectioner’s sugar and stir to coat. Slightly flatten the balls and then dip in the sugar again to coat well.
Arrange 2 inches apart on prepared cookie tray. Bake, until puffed and firm, about 16 to 18 minutes.