In brief
In a cake made by creaming butter, cold eggs can firm up some of the fat and make a uniform mixture harder to achieve.
Useful to know
In a cake made by creaming butter, cold eggs can firm up some of the fat and make a uniform mixture harder to achieve. King Arthur explains why some recipes explicitly call for eggs at room temperature. [1]
Follow the particular instruction, since other batters deliberately use cold ingredients. Prepare only the amount needed rather than turning a preparation requirement into a storage rule. Egg temperature and the order of addition are separate from the number of eggs. Equal quantities do not guarantee the same intermediate texture.
Sources
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