Preheat your oven to 350°F and prepare a standard 9×13″ baking pan by lining with parchment paper.
Melt the butter in a microwave-safe bowl or glass, heating in 30-second intervals until fully melted. Pour the melted butter into a medium mixing bowl, then add the granulated sugar. Use an electric or stand mixer to blend for 2-3 minutes until the mixture is smooth and well combined.
Gradually add the eggs, mixing in one at a time. Ensure each egg is fully incorporated before adding the next. Once combined, stir in the vanilla extract and salt until evenly mixed.
Add the flour and cocoa powder, mixing until fully combined. Gently fold in the chocolate chips, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan and set aside.
To begin the cookie layer, cream the butter and sugar together in a large bowl with your electric or stand mixer until it is light and fluffy.
Add in the egg and vanilla extract and beat the mixture well.
In a separate medium bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients from the medium bowl into the wet ingredients in the large bowl, mixing slowly to ensure even incorporation. Continue mixing until a smooth, soft dough forms. Finally, gently fold in the chocolate chips and mini Cadbury Eggs, making sure they are evenly distributed throughout the dough.
Use a dough scoop, spoon, or your hands to form the cookie dough into rounded balls. Grab your brownie pan and place the dough balls on top of the brownie layer, leaving small gaps between them to allow for even baking. Check out the video to see more details on spacing.
Bake at 350°F for 25-30 minutes, or until the cookie dough portions turn golden brown and the brownie layer is fully set. Carefully remove the brookies from the oven and let them cool for about 10-15 minutes before slicing into pieces for serving. Enjoy your Easter Brookies!