Melt the butter (1 cup) until golden. Add the dark brown sugar, white sugar, vanilla extract and expresso powder to the melted butter. Let it cool for a few minutes. To make it creamier, beat this mixture for about 10 min in a mixer.
Mix the dry ingredients in a bowl.
After the butter-sugar mixture has cooled down a bit, add the dry ingredients to it and later add the egg and yolk
Add the chocolate. Instead of using chocolate chips, there’s the option of chopping a chocolate bar. The amount is proportional to your love of chocolate!
Bake it for 12-15 min at 180°C