In a bowl, stir the butter with the white and brown sugar until creamy. Add the eggs one at a time and stir in each egg well. Add vanilla extract and salt and stir in.
Mix the flour, cocoa powder and baking soda in a second bowl and then stir into the creamy butter mixture. Carefully stir in 2/3 of the white chocolate chips.
Shape the dough into balls and place about 9 of them on a baking sheet lined with baking paper, leaving enough space between the balls as they run quite a bit. Distribute the remaining chocolate chips on the balls, pressing lightly.