01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside.
03 - Combine melted butter and brown sugar in a large mixing bowl. Stir until smooth and well incorporated.
04 - Beat in egg and vanilla extract until fully blended into the butter mixture.
05 - Gently fold dry ingredients into wet mixture using a spatula. Mix until just combined—avoid overmixing.
06 - Add white chocolate chips, milk chocolate chips, and chopped Cadbury Mini Eggs. Fold gently to distribute evenly.
07 - Spread batter evenly into prepared pan. Press reserved whole Mini Eggs onto surface, lightly embedding into batter.
08 - Bake 22 to 25 minutes until top is golden brown and a toothpick inserted in center shows moist crumbs.
09 - Cool completely in pan. Lift out using parchment paper overhang and cut into 12 equal squares.