1. Preheat the oven to 350 degrees F.

2. In a medium sized bowl combine flour, baking soda, baking powder and salt.

3. In a separate medium sized bowl add butter, sugars, vanilla, eggs and egg yolk. Stir until the eggs are fully incorporated.

4. Add the wet mixture to the dry mixture and gently stir until no flour streaks remain. 

5. Fold in Cadbury Mini Eggs until evenly distributed.

6. Spray a 9×13 pan with cooking spray.

7. Spread blondie batter evenly into prepared baking dish. 

8. Bake for 22-24 minutes until edges are a light golden brown color. Remove from the oven and let cool completely before cutting into squares.