Costco sells ingredients at scale, which means you can snag a 5‑lb bag of Kirkland Signature all‑purpose flour and a massive tub of chocolate chips for a fraction of regular prices. Buying in bulk eliminates the temptation to substitute lower‑quality items, giving you a stable foundation on which technique alone can shine.
The chemistry of a chocolate chip cookie pivots on moisture retention and fat crystallization. When butter is melted too early, the dough loses structure; when it’s too cold, it resists spreading. Likewise, an uneven chip distribution creates bite‑size gaps. Understanding these reactions lets you steer the bake toward the desired texture every time.