In a large bowl, add your melted butter, brown and granulated sugar, 2 eggs, and vanilla. With your hand mixer, beat on medium for 3 minutes scraping down the sides of the bowl as needed with your silicone spatula.

In a medium bowl, whisk your all-purpose/plain flour, cocoa powder, baking soda, and salt together.

Slowly pour your dry ingredients into your wet ingredients mixing together with the hand mixer. The batter will be very thick.

Pour in your milk and beat a little longer until incorporated into the batter.

Next, add the chocolate chips and mix in by hand.

Place your batter into the fridge and let chill for 3 hours.

Preheat your oven to 350℉/180℃/Gas Mark 4.

Line your cookie sheet with parchment paper. Remove your batter from the fridge and using a spoon or cookie scoop, scoop the batter and place onto the cookie sheet. Make sure that the cookies are taller than they are wide. This will ensure a nice thick cookie that is evenly baked.

Take your chocolate chunks and press a few into the tops of the cookies.

Place the cookies into the oven for 11-12 minutes. Because the cookies are so dark it will be hard to tell if the centres are baked, but if the edges are hardening then they will be baked properly.

Remove from the oven and let cool for 10 minutes before trying to transfer to a cooling rack as they will be quite soft in the middle.