Line a cookie sheet with parchment paper and preheat oven to 350 degrees F.
Using an electric hand mixer or stand mixer with a paddle attachment, beat butter and sugars for about 5 minutes until light and creamy.
Add the egg and vanilla to the butter-sugar mixture and continue beating using medium speed, until combined.
In a separate bowl, add the flour, baking soda, baking powder and salt and whisk until combined.
Slowly add flour mixture to wet ingredients and mix, using a spatula or low speed if using a mixer, until incorporated (do not overmix).
Fold in the chocolate chips and crushed Cadbury eggs (save some to decorate)
Portion the cookie batter using an ice cream scoop (2 tbsp) and place on a prepared baking sheet.
Add some extra crushed Cadbury eggs on top of each cookie and bake for about 13 minutes until the edges are golden brown and the middle is soft and chewy.
Let the cookies cool on the baking sheet for 5 minutes and enjoy!