Rosy - from Redwood City, CA
It sounds like your ingredients are not at room temperature when you are mixing everything together. For example, after you have creamed your butter and sugar, it is room temperature, light and fluffy; if you next add eggs that are cold, the butter will re-harden and look curdled. If the eggs are room temperature, the butter will remain smooth and fluffy. If you don’t have time to let the eggs sit at room temperature, the eggs can be placed in a bowl of warm water for 10-15 minutes before using – this should take the extreme chill off.