Preheat the oven to 350 degrees Fahrenheit.
Lightly grease the cookie sheets or line with nonstick baking liners.
In the bowl of an electric mixer, cream together butter, brown sugar and granulated sugar for 2 minutes on medium high speed, until light and fluffy.
Add in eggs and vanilla extract and mix until well combined and the mixture lightens in color, scraping down the sides of the bowl in between.
In a separate bowl, whisk together flour, baking cocoa, baking soda and salt.
Add the flour mixture to the wet mixture and mix just until incorporated.
Stir in the chocolate chips and crushed Reese's Eggs by hand.
Form or scoop the dough into 1 1/2" balls and place at least 2" apart on the cookie sheets.
Bake for 8 to 9 minutes, or just until set.
Let cool on the cookie sheets for a few minutes before carefully removing them to a cooling rack to cool completely. Press additional crushed Reese's Eggs in the top just after removing them from the oven, if desired.
Store in an airtight container after they're cooled completely to retain freshness.
