Line an 8 x 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
Heat-treat the flour to 165°F (74°C), then allow it to cool completely.
Beat the softened butter, granulated sugar, and brown sugar until smooth and creamy.
Mix in the milk and vanilla extract.
Add the cooled flour and salt, mixing until a soft cookie dough forms.
Fold in the chopped Circus Animal Cookies and rainbow sprinkles.
Press the cookie dough evenly into the prepared pan.
Refrigerate until the cookie dough layer is firm.
Melt the white chocolate chips with the heavy cream in short microwave intervals, stirring between each interval.
Stir in the vanilla extract until smooth.
Pour the white chocolate mixture over the chilled cookie dough and spread evenly.
Sprinkle the crushed Circus Animal Cookies and remaining sprinkles over the top
Refrigerate until the white chocolate layer is completely firm.
Lift the dessert from the pan using the parchment paper and cut into 16 bars.