Butter and eggs need to be at room temperature. If you’re in a hurry, throw the butter in the microwave at 50% power in 15 second intervals to warm it up. Place the eggs in a bowl of warm water for about 15-20 minutes to bring them to room temperature. The reason that you want to use room temp eggs and butter is because they won’t properly combine if they are cold. You’ve probably seen it happen – you add cold eggs to your smooth creamed butter and sugar and suddenly you have a lumpy soup. This can lead to little bits of butter that aren’t thoroughly mixed into the dough, which can cause problems later in the baking process.