In a medium bowl, whisk together the flour, cocoa powder, baking soda and salt.
In the bowl of a stand-up mixer, with the paddle attachment, add the butter and sugar; beat until light and fluffy, about 2 minutes. Add the egg and vanilla and beat until combined. In one batch, add the dry ingredients and cover the mixer with a clean kitchen towel. Turn on low and then turn to medium and mix until combined, about 40 seconds. Add the mini chocolate eggs and mix until combined.
Cover the bowl with plastic wrap and transfer the bowl of cookie dough to the fridge to chill for about 1 hour.
When the cookies are done chilling, preheat the oven to 350 degrees F.
Scoop cookies out onto cookie sheet lined with parchment paper, spacing them about 3 inches apart. Press the tops of them a bit with your hands. Bake for 10-12 minutes, or until the cookies are set in the center. These cookies are tough to tell when they’re done because you can’t tell if they’ve gotten brown so definitely watch the clock. Cool on a wire rack completely and then sprinkle the top with salt.