What should you do if you only have 1 egg and a recipe calls for 2?

buy more eggs cause if u use 1 the recipe might not work

Another Answer:

Use the single egg. If it is extra-large or jumbo size, don't worry about adding anything else. Your egg is large enough to do the job.

Now, if your egg is small, medium or large size, the substitution depends on the function of the egg in the recipe.

In baked goods, such as cookies and simple cakes, add 2 Tbs. water and 1 Tbs. vegetable oil. Alternatively, you could MASH half a banana to replace one egg, provided the taste would work with the recipe.

If the egg is thickening, such as in a sauce or custard, add 2 Tbs. cornstarch and 1 Tbs water.