Using too much baking soda or baking powder can really mess up a recipe, causing it to rise uncontrollably and taste terrible. But don't freak out if you accidentally poured too much baking soda in cookie dough or added too much baking powder to cake batter. Depending on the situation, you might be able to fix it. Try one of these solutions first before dumping all the ingredients and starting over.
Remove Unstirred Ingredients
If you catch your measurement error before you start stirring all your ingredients together, you might be able to simply scoop out all of the baking soda/powder and start again. This method will waste a bit of baking soda or powder, but it'll allow you to save the rest of your ingredients.
Increase the Quantity for an Easy Fix
If you know how much extra you added, just increase the other ingredients in the recipe to match the amount of baking soda or baking powder that you used. For example, if you accidentally used 1 teaspoon rather than the 1/2 teaspoon the recipe called for, just double all the other ingredients in the recipe, and you'll have a big batch of whatever it is you're baking. Then, proceed with the recipe as written.
It's typically easiest to double the recipe, especially if you're making a cake or bars. This may require a few tricky measurements and conversions, but it'll save you from having an awkward portion that is either too big or too small for your pan, or that requires a special oven time. If you're making cookies, you don't have to strictly double everything since the dough is divided into individual portions.
This isn't a perfect solution since it will give you a larger batch than you intended to make, require more of the other ingredients, and might require an extra pan or cookie sheet, but it sure beats tossing out all of those ingredients. Keep in mind that some cooked cakes freeze well as does most cookie dough.
When to Start Over
If you have no idea how much you threw into the mixing bowl, and you can't scoop it all out, tossing your ingredients out and starting again is probably your safest and best bet. While it's painful to waste ingredients, you probably won't be happy with the way your recipe turns out if you decide to move forward without dealing with the overdose of baking soda or baking powder. The only thing worse than wasting ingredients is wasting ingredients and time.
If your recipe called for mixing dry and wet ingredients separately, and you caught the mistake before they were combined, then you only have to begin again with the dry ingredients.
Reasons to Start Over
When you're cooking for the family, flops aren't a big deal. But when you're cooking for other people, you want your recipe to turn out right. If you're making something that you won't be able to taste before serving and/or won't have time to make again, you're probably better off just starting over when you realize your mistake. You want to be remembered for your baking successes—not your baking flops. If you're only baking for yourself and think the recipe might be salvageable (or don't care), go ahead and continue. See how the baked good turns out and learn from your mistakes.