01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang on sides for easy removal later.
02 - Whisk together flour, baking powder, and salt in a medium bowl until well blended. Set aside.
03 - Combine melted butter and brown sugar in a large mixing bowl. Stir until smooth and fully incorporated.
04 - Beat in egg and vanilla extract into the butter-sugar mixture until fully combined and smooth.
05 - Gently fold dry ingredients into wet mixture using a spatula. Mix just until combined—do not overmix to maintain tender texture.
06 - Fold in white chocolate chips, milk chocolate chips if using, and chopped Cadbury Mini Eggs until evenly distributed.
07 - Spread batter evenly into prepared pan. Press reserved whole Mini Eggs onto surface, gently embedding them into batter.
08 - Bake 22–25 minutes until top is golden brown and toothpick inserted in center comes out with moist crumbs (not wet batter).
09 - Cool completely in pan. Use parchment overhang to lift blondies out, then cut into 12 equal squares.