Vol. XXV · Cakes, Pastry and Sweets Plate 4 of 12cookies, biscuits, spread, chewy, crisp, butter temperature, chilling dough, white sugar, brown sugar, flour protein, chocolate chip cookies, 曲奇, 饼干MT

Cookies.

Chill a chocolate-chip cookie dough overnight and the cookies bake thicker, chewier and browner. The recipe did not change; the butter's temperature did.

A cookie dough is fat, sugar, flour and a little egg or liquid, and in the oven it melts before it sets. How far it spreads in that interval decides its shape and texture. Butter that is already soft spreads at once; chilled dough, whose butter is still mostly solid (IX.2), holds its shape longer while the edges set. White sugar dissolves in the dough's water and makes a syrup that spreads and then sets crisp as it dries; brown sugar, with its molasses and invert sugar (VII.9), holds water, browns faster and gives a chewy, soft centre; corn syrup or honey even more so. Flour sets the structure: more flour, or higher-protein flour, means less spread.

So the levers are: butter temperature (and creamed versus melted butter), the ratio of white to brown sugar, flour amount and protein, egg (more yolk richer and chewier, more white drier and cakier), and leavening (soda spreads and browns, powder puffs). Resting dough overnight also lets the flour hydrate and some sugar dissolve, giving deeper browning and a chewier texture. The workshop bakes a cookie.

Below: a teaching index of how far a cookie spreads from the dough temperature you choose (butter's solid fat at that temperature, course melting curve, IX.2), the share of white sugar and the flour, with the texture it tends to give.

What you will learn
Workshop
Teaching index: spread = (1 − butter solid fraction at the dough temperature) × (0.6 + 0.4 × white-sugar share) × flour factor (cake 1.1, all-purpose 1, bread 0.85), scaled to 1 for warm dough with all white sugar. Butter solid fraction from the course melting curve (IX.2).

Cold for thick, warm for thin; brown for chew

On the teaching index, dough at 20 °C with half white, half brown sugar spreads to 0.73; chilled to 5 °C, only 0.26, because about two-thirds of the butter is still solid when it goes in. At 20 °C, all white sugar gives 0.91 and all brown 0.55. Real cookies also depend on the oven (a hotter oven sets edges before spreading) and the tray (a cold tray spreads less), but the order holds.

Recipes for each texture: thin and crisp — melted or very soft butter, mostly white sugar, a little extra water or milk, all-purpose flour, bake until golden throughout. Thick and chewy — cool creamed butter, mostly brown sugar, an extra yolk, a little bread flour, scoop tall, chill an hour or overnight, bake until just set at the centre. Cakey — more egg, baking powder rather than soda, cake flour. Bake on parchment, rotate trays halfway, and let cookies firm on the tray for a few minutes: they are soft when hot and set as their sugar cools (VII.7).

At the stove

Bake two cookies from one dough: one scooped straight away, one after chilling the dough overnight. Compare spread, thickness and colour.

The chocolate chip cookie was invented around 1938 by Ruth Graves Wakefield at the Toll House Inn in Massachusetts; Chinese bakeries' 曲奇 takes its name from "cookie" and is usually a piped butter biscuit closer to Danish butter cookies.

Terms

Spread
How far a cookie flows before it sets.
Brown sugar
Sugar with molasses; holds water and browns fast.
Chilling dough
Resting dough cold so the butter firms and the flour hydrates.
Cakey
Soft, light cookies with more egg and powder.
Cookies spread as their fat melts before they set. Chilled dough, brown sugar and more or stronger flour keep them thick and chewy; warm butter and white sugar make them thin and crisp.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.