Preheat your oven to 410 degrees Fahrenheit.

In a big bowl, let's start by creaming together the cold butter and sugars until it's light and fluffy – takes about 4 minutes. Add the eggs one at a time, making sure to mix well after each addition.

Time to bring in the chocolatey magic! Add the dark baking cocoa, cake flour, all-purpose flour, cornstarch, baking soda, and salt. Stir it all up until it's beautifully combined. Now, fold in those delicious semisweet chocolate chips.

Give your dough a little chill time – about 15 minutes should do the trick.

Now, let's shape the dough into some generous balls and place them on a lightly colored cookie sheet. If you're feeling fancy with a scale, aim for cookies ranging from 4.5 to 6 ounces. You'll fit 4-6 cookies on one large sheet, and trust me, it's worth it. This dough makes 8-12 extra-large cookies.

Into the oven they go! Bake for 9-11 minutes or until they sport a lovely golden brown on top. Once they're out, let these beauties rest for at least 10-15 minutes to set.