Preheat oven to 400° degrees F.
Line 2 baking sheets with parchment paper.
In a mixer, beat butter and sugar. .
Add eggs and vanilla.
Add cocoa powder, cornstarch, baking soda, salt, cake flour, and all-purpose flour.
Mix on low and fold in the chips.
Chill 15 mins.
Use a food scale and measure out 6 ounces of dough for each cookie. Flatten a bit.
Bake approx 12 mins and let cool on sheet.
They will firm up as they cool.