Preheat the oven to 180ºC . Lightly butter a cookie sheet, or alternatively, line the sheet with a strip of parchment paper.Set aside. In a mixing bowl, mix together the flour, cocoa powder and baking soda. Set aside. Using an electric mixer or a hand-held beater, cream the butter and sugars until the mixture is light and fluffy. Add the eggs and continue to beat until they are well-combined, about 1 minute. Mix in the flour, cocoa powder and baking soda mixture until well incorporated. Fold in the white chocolate chunks with a rubber spatula. Filling a tablespoon, scoop out individual cookies from the batter and place in even rows on the cookie sheet, leaving 5 cm of space between each cookie.
Transfer the cookie sheet to the middle shelf of the oven, and bake for 8-10 minutes until the cookies are puffed and still to the touch.
Remove the cookie sheet from the oven and allow cookies to cool and set for 5-7 minutes before carefully removing them with a spatula. If you have used a sheet of parchment paper, slide the entire sheet off the tray, and allow the cookies to cool for 5-7 minutes. Meanwhile, you may re-use the cookie sheet immediately for baking the next batch.
*NOTES*
These rich brown cookies studded with chunks of white chocolate are a delicious, inside-out version of chocolate chip cookies. Since the cookie batter is brown to begin with, you won't be able to use their toasty color as a visual indication of doneness. To avoid overcooking, remove the cookies from the oven as soon as they puff up and are still slightly soft to the touch. The cookies will set as they cool, but should remain pliable rather than hard or crunchy.