Rescues · TO BAKE
Cookies spread flat into one thin sheet.
Why it happens
The butter was too warm, so it melted and ran before the flour's structure could set around it. Softened butter is cool to the touch and just pliable, never shiny. Chilling the shaped dough firms the fat back up; too little flour, too much sugar, or a hot greased pan all push in the same flat direction.
Recovering it
An underbaked centre can go back in, covered with foil so the crust stops darkening — this works far more often than people expect. A sunken cake cannot be re-risen; it is still perfectly edible and is best repurposed as a trifle or a pudding base. Overbaked and dry is masked by syrup or cream and not fixed. The durable answer to uneven baking is an oven thermometer, because most ovens are not the temperature their dial claims.
The mechanism
In baking, heat is setting a structure rather than cooking something already formed. Several changes happen at once and in order. Gases expand and steam forms, inflating whatever the batter or dough has trapped — most of a cake's rise happens in the first minutes and is oven spring, not leavening acting later. Starch gelatinises from around 60°C, absorbing water and swelling. Egg and gluten proteins coagulate from roughly 70°C and lock the expanded structure in place. Only above about 150°C does the surface brown. Opening the door early drops the temperature and can collapse a structure that has expanded but not yet set — that is the real reason the warning exists, not superstition. Sugar, dairy and egg all brown fast, which is why enriched doughs bake cooler than lean ones.
The full TO BAKE lesson — how to tell, where to practise it, what it carries to.