Add the softened butter to a mixing bowl.
Add the granulated sugar and mix until creamy.
Add the brown sugar and mix until well combined.
Add the egg and egg yolk and mix until fully incorporated.
Add the vanilla extract and mix well.
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture.
Mix until a soft dough forms.
Add the crushed biscuits and white chocolate chips and mix until evenly distributed.
Add the rainbow sprinkles and gently mix into the dough.
Scoop portions of dough onto a parchment-lined baking sheet and gently flatten them.
Bake at 350°F (175°C) for 10–12 minutes, or until the edges are lightly golden.
Remove from the oven and allow the cookies to cool completely on a wire rack.
Melt the white chocolate with the heavy cream and stir until smooth.
Dip the cooled cookies into the white chocolate glaze.
Sprinkle rainbow sprinkles over the glazed cookies.
Allow the glaze to set completely.
Serve and enjoy.
