01 -
In a mixer bowl fitted with a paddle attachment, cream together unsalted butter, brown sugar, and granulated sugar on medium speed until smooth, approximately 1 minute.
02 -
Beat in the egg and vanilla extract until fully combined.
03 -
Whisk together all-purpose flour, cocoa powder, baking soda, espresso powder if using, and salt in a separate large bowl.
04 -
Add the dry mixture into the butter mixture and mix on medium-low speed until just combined, about 30 seconds.
05 -
Fold in mini chocolate eggs and chopped dark chocolate on low speed until evenly distributed; the dough will be sticky.
06 -
Cover the dough bowl with plastic wrap and refrigerate for 30 to 45 minutes until firm to the touch.
07 -
Preheat the oven to 175°C (350°F). Line a baking sheet with parchment paper.
08 -
Use an ice cream scoop to portion chilled dough onto the parchment-lined baking sheet. Sprinkle each dough ball with flaked sea salt.
09 -
Bake at 175°C (350°F) for 10 to 12 minutes. Allow cookies to rest on the baking sheet for 15 minutes before transferring to a cooling rack to cool completely.