Mix ingredients just until combined after adding the cake mix to prevent overdeveloping gluten, which will make cookies tough instead of soft and chewy.

Let eggs sit out for 30 minutes before mixing to ensure they blend smoothly with oil and butter, creating a more uniform, moist texture throughout.

Refrigerate the dough for at least 2 hours to prevent spreading and help cookies maintain their thick, fudgy center while the edges set properly.

Remove cookies when edges are set but centers still look slightly underdone—they'll continue cooking on the hot pan for that perfect Texas sheet cake-style chewiness.

Combine these dry ingredients before mixing with wet ingredients to eliminate lumps and ensure even chocolate flavor distribution throughout every cookie.