Line a baking sheet with parchment paper or wax paper.
If using chocolate bars, chop the white chocolate into small pieces for even melting. Heat in microwave for 20–30 second intervals, stirring between each until smooth.
Divide the melted white chocolate evenly into three bowls. Use the candy coloring to tint one portion dark pink, and one portion light pink. Leave the final portion white.
Spoon large dollops of each color of melted chocolate randomly across the lined baking sheet. Alternate the colors to help create a marbled effect. Using a knife or toothpick, gently swirl the chocolate in circular motions across the pan. Be careful not to overmix. A few light swirls will give you that beautiful marbled white chocolate bark look. Use a spatula to spread it into an even layer about 1/4-inch thick.
Immediately add your frosted circus animal cookies and sprinkles. Press larger pieces in gently so they stick.
Refrigerate for 20–30 minutes, or until fully hardened.
Once set, break the bark into irregular pieces by hand or cut with a sharp knife.
Notes
Double Boiler Method: Place a heat-safe bowl over a pot of simmering water. Stir continuously until melted.