Measure out about 1 cup of whole Cadbury mini eggs. Place in a plastic freezer bag and close. Then bash with a rolling pin or other heavy objects a few times to crush up the eggs. Then set aside.
In a medium size mixing bowl combine flour, corn starch, salt, baking powder and baking soda. Stir until well combined and set aside.
In the bowl of a stand mixer (or mixing bowl with a hand mixer) add butter and cream on medium high speed for a minute or two until fluffy. Add white granulated sugar and brown sugar and mix on medium high speed for about 2 minutes until fluffy and well combined.With the mixer on low speed, add in vanilla extract and egg. Then turn up to medium speed for 15-30 seconds until well combined, scraping down the sides as needed.
Add in about half of the flour mixture and mix on medium speed for 15-30 seconds. Then add in the remaining flour mixture and blend on medium speed for another 15-30 seconds until just combined. Do not over mix.Finally, add in the chocolate chips and crushed Cadbury mini eggs. Mix on the lowest speed for about 15-30 seconds until well distributed.
Cover the mixture with cling film and refrigerate for at least 2 hours.
When you are ready to bake the cookies preheat the oven to 350 degrees F. Place the remaining ½ cup of mini eggs on a cutting board and use a knife to roughly cut them in half. Set aside.
Using a cookie scoop, measure out about 2 tablespoon of dough and place on a parchment paper lined baking sheet about 2 inches apart. Bake the cookies at 350 degrees for 10 minutes then remove from the oven. Allow the cookies to cool on the baking sheet for about 5 minutes before transferring the cookies to a wire rack to cool completely.
While the cookies are cooling but still warm, press a few pieces of the chopped mini eggs on the top. You can also sprinkle on some flaky sea salt if desired. Wait for the cookies to cool completely and then serve. Enjoy!