I need help D: I'm making 300 yellow cupcakes for prom in 2 days and I've purchase salted butter instead of unsalted . - Can I use the salted butter instead of using unsalted and just not add in salt ?
Yes, you should be able to get away with it, but it does depend on how salty the butter is. Might be worth making one batch and seeing how it turns out.
I'm very far from being an expert in the kitchen, so take this with a grain of salt (sorry), but:
Unsalted butter has a negligible amount of sodium. Table salt has about 2400 milligrams of sodium per teaspoon. Different salted butters have differing amounts of salt, so check your salted butter's label for the sodium content. If the amount of butter you're using has, say, 600 milligrams of sodium, figure that's about a quarter of a teaspoon of salt, and reduce the salt in your recipe accordingly.
Or see if the supermarket will allow you to exchange the salted butter for unsalted.
The folks at Cook's Illustrated had this to say to a similar quesiton:
We advise against cooking with salted butter for three reasons. First, the amount of salt in salted butter varies from brand to brand—it can range from 1.25 percent to 1.75 percent of the total weight, making it impossible to offer conversion amounts that will work with all brands. Second, because salt masks some of the flavor nuances found in butter, salted butter tastes different from unsalted butter. Finally, salted butter almost always contains more water than unsalted butter. The water in butter ranges from 10 to 18 percent. In baking, butter with a low water content is preferred, since excess water can interfere with the development of gluten. In fact, when we used the same brand of both salted and unsalted butter to make brownies and drop biscuits, tasters noticed that samples made with salted butter were a little mushy and pasty; they preferred the texture of baked goods made with unsalted butter.
However, if it's all you have, I wouldn't worry too much. Just reduce the salt called for in your recipe by 1.7 grams or 1/3 of a teaspoon (table salt) for each 8 tablespoons (stick) of salted butter you use. This is the average amount of salt in a stick of salted butter.