In a medium sauce pan melt the butter. Once the butter is melted allow it to boil. Keep an eye on it as it will boil and then thick white foam will appear on top. Listen closely, once the butter stops making any popping noise, the butter is browned. Take off of the heat. Stir and you should see little brown bits and smell a nutty aroma.
Allow the browned butter to cool in a large mixing bowl.
Once cooled, add in the brown sugar and granulated sugar. Stir until combined.
Add in the eggs and vanilla, mix until combined.
Pour in the flour, baking soda, and salt. Mix until combined and a dough is formed.
In a large plastic Ziploc bag, add the Cadbury eggs. Hit with a rolling pin to break the eggs up into smaller chunks. Pour the broken eggs into the dough and fold in.
Scoop the dough onto a few light metal, parchment paper lined cookie sheets.
Bake for 8 minutes. Remove and allow them to cool before enjoying!