While some people are content enjoying gorgeous fluffy omelettes and rich, eggy custards, others prefer to get their sustenance elsewhere. Some might be avoiding fats or cholesterol, others might be vegan or vegetarian and want to avoid eggs as well as meat, but for those who don't like to nosh on ovum, it can be difficult to replace them - particularly in baked goods and sauces.

There are some tried and true options that I've seen used from time to time, but determining which is best to use depends on the outcome you'd like to get. Three options: flax seeds, silken tofu, and mashed banana are tested here in the same recipe - scoochmaroo's awesome chocolate chip cookie recipe.

Step 1: Options, Options

Different egg substitutes can be utilized to get a variety of results in all sorts of applications, but the choice of which to use depends on what role eggs need to play in the recipe. In cakes, for example, eggs are used to leaven the batter and make the cake fluffier. Cookies and muffins depend on eggs to add moisture and bind the batter together, while sauces and savory dishes usually rely on eggs for consistency and texture.

In addition to the examples below, there are loads of other things that folks use to replace eggs for whatever reason, including commercial egg replacers.

Silken Tofu¹
Perfect for replacing eggs in sauces² or adding to frosting for cakes, silken tofu is also great in baked goods. It can make baked goods a little bit heavy but will keep them nice and moist, so it's better in brownies rather than angel food cake.

Use 1/4 cup silken tofu to replace each egg in a recipe
Great for: cakes, cookies, brownies, sauces
How: The high protein content in both eggs and tofu make them ideal thickeners, in addition to the fact that they also emulsify well into other ingredients so you're not left with weird lumps and bumps. Upon being heated, protein thickeners like eggs or tofu unwind and then (if at high enough concentrations in the liquid they've been added to) when they begin to cool they set up and make the mixture more solidified.

Flax Seed
Adding a slightly nutty flavor, flax seed is wonderful for heavy or dense baked goods.

Use 1 teaspoon of ground flax seeds and 1/4 cup water to replace each egg in a recipe (grind flax seeds and combine with water - let sit for a minute or so before adding to a recipe)
Great for: waffles, pancakes, bread, cookies (particularly oatmeal cookies)
How: For the same reason the flax can aid in digestion, the stickiness and slimey-ness created when ground flax and a liquid are combined make them an ideal egg replacement. Some people even use flax slime for hair gel! The slime is the result of the oils of the flax seeds combining with moisture, and can even happen if the seeds are kept in too humid of an environment. The slime also makes flax an idea replacement for gluten (when combined with several eggs).

Pureed/Mashed Fruit
Mashed bananas, applesauce, or other fruits can be used in muffins and other treats. I personally prefer to use bananas in things like cookies and applesauce in cakes or things where you're aiming for a more pudding-ish outcome. The end result will be rich, moist, and quite dense (so if you want to lighten things up a little, add a touch of extra baking soda). You may want to add a little extra baking time to help balance out the extra moisture that fruit can add.

Use 1/4 cup of mashed banana (usually about a half banana) or applesauce to replace each egg in a recipe
Great for: quick breads (like banana bread!), brownies, cakes
How: Mashed fruits provide a fair amount of moisture to recipes (as eggs would), and also serve to activate the gluten in flour and bind doughs, etc. together. Unlike eggs, they don't have a ton of "stickiness" of their own and so it can be difficult to get some doughs to hold together using only fruit.

Vinegar and Baking Soda
While not a great option in cookies, sauces, or savory dishes, a vinegar and baking soda combo works very well in cake recipes to keep cakes fluffy and light.

Use 1 teaspoon baking soda and 1 tablespoon of vinegar to replace each egg in a recipe
Great for: cakes
How: More like whipped eggs, the combination of vinegar and baking soda results in a reaction that will really blow the roof off your batter. For the same reason you might use baking soda and vinegar to clear a drain, the combination of acetic acid (what makes vinegar vinegar) and sodium bicarbonate (baking soda) results in the formation of carbonic acid, the bi-product of which is a release of carbon dioxide gas (the bubbles that are produced).

¹In addition to silken tofu, firm and extra-firm tofu can be used when making egg-free versions of dishes like quiche or egg salad, or even yummy tofu scrambles!
²I don't know if I could ever get by without the joy that is Hollandaise sauce (which can be made in the microwave!), but this is an awesome alternative (and it would be great with some eggplant bacon on the side).

Step 2: Rolling in Dough

In order to do a side-by-side comparison, I whipped up a half-batch of chocolate chip cookie dough, dividing it into quarters and substituting flax seed, tofu, and banana for the egg portion in each.

Scoochmaroo's Best Ever Chocolate Chip Cookie Recipe

1 1/4 cup flour
scant 1/2 teaspoon baking soda
large pinch salt
1/2 cup butter, softened (substitute with vegan butter substitute if making vegan)
1/2 cup brown sugar
3/8 cup sugar
1/2 teaspoon vanilla
1 egg (1 teaspoon ground flax seed and 1/4 cup water, 1/4 cup silken tofu, 1/4 cup mashed banana)
7 ounces chopped chocolate

Following the recipe instructions, I combined the butter, brown sugar, and sugar, and then separated the mixture into four portions. I added 1/4 of the egg substitutes, one into each quarter of dough, and then added the remaining ingredients as instructed. Using a cookie scoop, I portioned out the dough on a foil lined cookie sheet and popped it in the freezer over night (this helps allow the gluten in the dough to relax and ensures that the cookies won't be tough when baked). The next morning, I baked the cookies at 350 degrees Fahrenheit for 9 minutes.

Step 3: Results

Flax

Most similar to the cookie made with egg in terms of texture and flavor
Light but not too puffy, with a slightly nutty taste

Banana

Soft and chewy
Pleasant, but banana flavor is present

Tofu

Moist and soft, but a bit too puffy for my taste
Slight change in flavor

In the future, I'll probably stick with flax seed if I need to replace the eggs in this particular recipe, but for other applications, that might not be the case. In a creamy sauce, for example, silken tofu would most certainly be my selection, and in a loaf of banana bread, bananas would be the obvious choice - it all depends on what you're whipping up and how you need your egg (replacement) to work.