In the bowl of a stand mixer and a paddle attachment, cream the cold butter, sugars, vanilla, salt, nutmeg, baking powder and baking soda on low speed.
Slowly increase the speed from low to medium and beat for at least 10 minutes, until the dough is fluffy and the soft. Stop the mixer half way to scrape down the bowl.
Add the eggs one at a time while the mixer is still running, beating well after each addition.
While the mixer is on low, slowly pour in both flours.
Fold in the chocolate chips and halva.
Weight out each cookie to be 6 ounces (170 grams) and shape into rounds. Wrap each cookie in plastic wrap and refrigerate for 12 hours, but preferably overnight.
Preheat you oven to 400°F/200°C and line a baking tray with parchment paper. Bake the cookies 3 at a time for 12-15 minutes.
Let the cookies rest for 15 minutes before eating.