Preheat oven to 400℉ and line a baking sheet with parchment paper. Set aside.
In a large bowl, combine melted butter, cocoa powder, espresso powder, brown sugar and granulated sugar. Whisk until smooth. It's okay if the sugars aren't fully dissolved, but there should be no lumps.
Add egg and vanilla extract. Whisk until smooth.
Add flour, salt, baking soda, coconut and Cadbury eggs. Fold until just combined (no visible flour streaks). The cookie dough will be sticky.
Scoop 1.5 tbsp cookies onto the baking sheet, placing at 3 inches (8cm) apart.
Bake for 7-8 minutes, until the centers no longer looks wet and the edges are light golden brown. They will lighten to the same colour as the edges. As soon as this happens, take the cookies out, they will continue to cook as they cool.
Let cool fully before enjoying. They need to cool so they can set and you can pick them up without them falling apart.