Try this How to Soften Butter recipe, or contribute your own.
Properly softened butter yields a uniform matte surface that yields immediately to light pressure without showing any translucent or oily puddles. Achieving this state requires balancing emulsion integrity against thermal conductivity. Butter consists of approximately 80 to 82 percent butterfat, 16 to 18 percent water, and about 1 to 2 percent milk solids. The crystalline network of saturated and unsaturated fats traps microscopic water droplets within a solid matrix. When heat is applied too aggressively, that crystalline structure collapses entirely, separating the liquid fat from the aqueous phase and ruining creaming capabilities. The ideal target temperature for baking sits precisely between 65 and 68 degrees Fahrenheit. At this thermal window, the fat crystals remain semi-solid while possessing enough plasticity to trap air bubbles when beaten with sugar. Microwave heating creates localized hot spots exceeding 100 degrees Fahrenheit because microwave radiation targets polar water molecules unevenly, rapidly liquifying pockets before the surrounding block thaws. Ambient counter tempering takes roughly 30 to 45 minutes depending on ambient kitchen temperature and initial stick thickness, provided the block is sliced into thin pats to maximize surface area exposure. Cold butter cannot incorporate air efficiently, which results in dense cakes and flat cookies lacking proper structural rise. Conversely, melted butter saturates flour proteins prematurely, yielding tough, greasy textures instead of tender crumb structures. Leftover softened butter should be tightly wrapped in parchment paper and returned to refrigeration within two hours to prevent oxidation and rancidity of the delicate surface fats, though it may be stored safely at 40 degrees Fahrenheit for up to three weeks.