Instructions

1. Cut the butter into cubes and let it soften at room temperature.
   
2. In a large bowl, beat the softened butter, sugar, and egg together with an electric mixer for 2-3 minutes until well combined.
   
3. Add the flour, chocolate chips, cocoa powder, and baking soda. Stir with a fork until combined, then knead by hand until you have a smooth dough.
   
4. Form the dough into a ball, wrap it in plastic wrap, and refrigerate for 30 minutes.
   
5. After 30 minutes, preheat the oven to 180°C/350°F (160°C/320°F if using a ventilated oven).
   
6. Remove the dough from the refrigerator. Take small portions of dough, shape them into balls about 4-5 centimeters (about 2 inches) in diameter, and slightly flatten them to form cookies. Place the cookies on a baking sheet, spaced slightly apart.
   
7. Bake the cookies in the preheated oven until ready, about 10 minutes (8-9 minutes in a ventilated oven).