Preheat the oven to 170 degrees celsius (340 Fahrenheit).
Melt the chocolate and butter and set aside to cool.
Add the eggs and sugars in the bowl of an electric mixer fitted with a whisk attachment and whisk until light and creamy and the mixture forms creamy ribbons.
Fold in the melted chocolate and butter mixture. Note, it's important the chocolate mixture is allowed to cool before being added to the eggs. If it's too hot this will make the mixture too liquid.
Sift in the flour, cocoa and baking soda and fold through the batter before adding the chocolate chips.
Drop spoonfuls of the batter onto a baking sheet lined with baking paper and bake for 8 to 10 minutes.