Creaming butter & sugar · The World Table

From the Lexicon, Creaming, Foaming & Cake Structure

Cakes rise on air you built before the oven. CREAMING: beating butter and sugar until pale: sugar crystals literally cut air pockets into the fat, which chemical leaveners then inflate (butter cakes, cookies where the long cream = lift). FOAMING: whipping eggs (whole: genoise; whites: meringue, angel food, chiffon) into a protein foam, the sponge family's entire structure. RIBBON STAGE: whole eggs and sugar whipped until the batter falls in a slowly-dissolving ribbon, the doneness test for sponges and molten cakes alike. The corollary rule: once air is in, FOLD, never stir: every rough stroke is height surrendered.

Read it in the Lexicon →

How to tell it is going right

The butter started at the right temperature: it took a fingerprint and held its shape, neither greasy and slumping nor hard from the fridge.
It has visibly paled, from yellow towards near-white, and grown in volume, and getting there took minutes rather than seconds.
The texture is light and aerated: a spoonful is fluffy and holds a soft peak rather than sitting dense on the spoon.
Rubbed between finger and thumb it is still faintly gritty with undissolved sugar, and not slick or oily.
It is one homogeneous cream: not split, slackened, or separating into a greasy mass with liquid running out of it.

Where it goes wrong The butter was too warm, or it was beaten well past its point, so the fat softened and gave up the air it had taken: the mixture goes slack and oily and the cake bakes dense and greasy with a sunken middle.

A chosen film How to Cream Butter and Sugar | Food Network Food Network Watch for: The colour change in the bowl: butter going from yellow and dense to pale and visibly increased in volume, which is the air you are building before any leavener gets a chance to work.