Line 2 large baking trays. Place the butter and sugars in a large bowl and cream together until smooth. 

Add the egg and Vanilla Extract and beat into the mixture until all combined. Sift the flour, Cocoa Powder and Bicarbonate of Soda on top and fold into the mixture to create a dough.

Finally add the chopped White and Dark Chocolate and stir into the cookie dough.

Divide the cookie dough into 12 equal pieces and roll each pieces into a ball. Working on one piece at a time take the ball of dough and using your thumb push a hole in the centre. Add 2 cubes of milk chocolate into the hole and wrap the cookie dough around the chocolate to ensure it is completely covered. Place on the prepared baking tray. Repeat this for each pieces of cookie dough and then chill in the fridge for 30 minutes.

10 minutes before baking preheat the oven to 190°C/170°C/Gas mark 5. Once chilled place the cookie dough balls into the oven and bake for 15-20 minutes. The cookies will still be soft once baked; they will firm up slightly whilst cooling. Leave to cool on the tray to cool for 10 minutes.

The cookies are best served warm for the ultimate gooey chocolatey centre! You can reheat the cookies in the microwave for 30 seconds.