Preheat oven to 350 degrees F. Line two baking sheets with parchment paper and set aside.
In a large mixing bowl, whisk together the brown sugar, granulated sugar, and egg until light.
Add the melted and slightly cooled butter to the bowl. Beat for 2-3 minutes, or until pale and creamy. Add the vanilla and mix to combine.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Add the flour mixture into the sugar/butter mixture and mix with a rubber spatula or wooden spoon until there are no more dry spots.
Once the cookie dough comes together, add the chopped chocolate and chopped mini eggs. Mix until the chocolate is evenly distributed.
Use a large cookie scoop to drop 3-4 tablespoon-sized dough balls onto a parchment lined baking sheet. At this point, you can cover the cookie dough tightly with plastic wrap and chill for at least 1 hour or up to 48 hours. If you don't have time, continue with the remaining steps. *Note: If you DON'T chill the cookie dough, your cookies will be thinner.
Arrange 5 cookie dough balls onto parchment lined cookie sheets.
Bake the cookies in a fully preheated oven for 12-14 minutes, or until the edges are set and the centers are slightly underbaked.
Cool on the pans for 5 minutes before transferring to wire racks.
Top the cookies with more chopped mini eggs and enjoy!