You're in the middle of baking, the dough fails to rise, and you realize that you forgot to add the yeast. As long as you haven't put it in the oven yet, there's an easy fix.
How to Add Yeast to Dough
If you forgot to add yeast to your dough, you can just mix the yeast called for in the recipe with a few tablespoons of warm (but not hot) water. Let it sit for five to 10 minutes. Once the yeast has activated, fold it into your dough, and allow it to rise.
When Yeast Goes Bad
However, you may not be as forgetful as you thought. A failed activation, paired with a failed rise, suggests that your yeast might have gone bad. Buy a new package of yeast, or use a yeast substitute as a stand-in until you're able to get to the store for more. Using a substitute will alter your recipe, but if you're just making pizza dough or rolls for a family meal, the results should be more than satisfactory.
An opened package of yeast will usually keep in the fridge for three to four months before it needs to be replaced. If you don't ever seem to use yours up that quickly, consider storing it in the freezer instead. Yeast keeps indefinitely there, and it doesn't need to be thawed or brought to room temperature before you use it. As soon as you add it to warm water, the yeast will spring back to life.
Add the Yeast Anyway
If you don't have time to wait for your dough to go through another rise plus however long it needs to spend in the oven, just add the yeast. Shape your dough into a neat ball, wrap it up tightly, and tuck it in the fridge. This will keep the dough from rising until you're ready to work with it—even if that's tomorrow or two days from now.
To use your dough, just pull it out of the fridge, and place it on the kitchen counter. It'll start to rise as soon as it comes to room temperature. Want to back-burner your baking project for more than a few days? Then, toss your dough in the freezer. Once it thaws, it will go through its normal rise.
Tips and Tricks
Get in the habit of proofing your yeast before you use it. This simple step allows you to verify that your yeast is good before you add it to your dough. This yeast fix isn't the only cooking hack you can use. Most kitchen mistakes can be undone with a few tricks.
For example, if you added too much baking powder or baking soda, just increase the other ingredients in the recipe to match the amount of baking soda/baking powder that you used if you know how much extra you added. The real trick is to know that with baking, there's almost always a quick and inexpensive (or free) fix for any problem.