The butter and eggs should not be completely chilled from the fridge, but should also not be room temperature. I try to let them sit out for about 15-30 minutes before I begin my cookie making!
Feel free to substitute with any kind of chocolate that you prefer.
I have given both cups and grams as measurements. Grams will be more precise, especially when measuring flour. If you don’t have a kitchen scale, no problem! Just lightly spoon flour into your measuring cup to insure its not packed in there. Light and fluffy is the key.