Preheat oven to 350 degrees F. Line a baking sheet with parchment paper, set aside.
With the paddle attachment, beat together the butter, brown sugar + granulated sugar until light and fluffy.
Add the full egg and beat until smooth, add egg yolk and vanilla, beat until smooth about 2 minutes.
Add flour, corn starch, baking powder, baking soda + salt and mix until just combined.
Roughly chop up mini eggs, fold into batter. Do not over mix.
Scoop cookie dough balls in about 2-3 tablespoons onto a parchment lined cookie sheet. Sprinkle with more chopped mini eggs, if desired.
Bake for 12 - 14 minutes and repeat with remaining dough. Allow cookies to fully set before moving off of pan – about 5 minutes. Enjoy!
These are best served at room temperature. You'll be tempted to eat them hot, but I promise they will be worth the wait.