Begin by sifting together 1 cup of all-purpose flour, ½ cup of cocoa powder, ½ teaspoon of baking soda, ¼ teaspoon of espresso powder, ½ teaspoon of salt, and ½ teaspoon of ground cinnamon into a large mixing bowl. Set aside with 1 cup of chopped dark chocolate and 1 cup of Cadbury mini eggs.

In a separate mixing bowl, beat ½ cup of softened unsalted butter, ½ cup of packed brown sugar, and ½ cup of granulated sugar together on medium speed for about 1 minute, until light and fluffy.

Add in 1 large egg and 1 teaspoon of vanilla extract to the butter-sugar mixture. Mix on low speed for approximately 30 seconds until smooth.

Gradually incorporate the sifted dry ingredients into the wet mixture, mixing on low until just combined—about 30 seconds.

Gently fold in the chopped dark chocolate and 1 cup of Cadbury mini eggs until evenly distributed.

Cover the cookie dough bowl with plastic wrap and refrigerate for 30 to 45 minutes.

While the dough chills, preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

After chilling, scoop rounded portions of the dough onto the prepared baking sheet, spacing them about 2 inches apart. Sprinkle a pinch of flaked salt on top.

Bake the cookies in your preheated oven for 10-12 minutes until the edges appear set while the centers remain slightly underdone.

Once baked, let the cookies rest on the baking sheet for about 15 minutes before transferring them to a wire rack to cool completely.