Preheat the oven to 180C / 350F, and line two baking sheets with parchment paper.
Break the dark and white chocolate into small chunks and crush the Easter mini eggs. To crush the min eggs, I put them in a plastic bag and use the rolling pin to crush them; you can also use a pestle and mortar to crush them.
Make the cookie batter: Whisk the butter, light brown sugar, and caster sugar in a large bowl until it is fluffy. Then whisk in the egg and vanilla extract until combined.
Mix the dry ingredients: In a separate bowl, add the flour, baking soda, and salt.
Mix wet and dry ingredients: Combine the dry ingredients with the butter mixture until well incorporated.
Add the chocolate and Cadbury mini eggs: Fold the chocolate chunks and crushed mini eggs into the cookie batter using a spatula or wooden spoon.
Shape the cookie balls: Use a medium cookie scoop or just scoop about 1 tablespoon of the batter per cookie into the baking sheets (make sure you leave space between each one).
Decorate: Press the remaining mini egg pieces on the tops of these cookies.
Baking: Bake the cookies in the preheated oven for 10 to 15 minutes. Let them cool on the counter for 10 to 15 minutes before transferring them to a wire rack to cool completely.
Notes
Store these cookies in an airtight container in the fridge for 5-6 days.
These cookies can be frozen for up to 3 months. I advise you to separate each cookie with baking paper before storing.