Butter is the main ingredient in almost all traditional baking recipes. It's used for breads, brownies, cakes, cookies, cupcakes, quick breads, and just about everything else. Most dairy-free recipes will use dairy-free substitutes, such as oil, soy margarine, or shortening, to stand in for butter in a given recipe. For health reasons, many people prefer to use liquid oils, such as canola and olive oil, in place of butter for dairy-free baking. In many cases, this will still produce fabulous results—however, it is also often the case that oil cannot stand in for butter on its own.
Why Butter Is so Important in Baking
To understand how to properly substitute for butter, it is important to understand how butter functions in various baking recipes. In most recipes for cakes, cupcakes, and quick breads, the process of creaming butter with granulated sugar is extremely important to achieving the even-rising, rich, spongy texture that characterizes these products. It is during the 3 to 5 minutes of beating the sugar into the butter until it is "fluffy" that the sugar granules aerate the dense fat. This gives cakes a rich texture and flavor that will also rise.
Baking Cakes Without Butter
It is because of this creaming step that using oil instead of butter for baking can be problematic.
Coconut oil, however, really is a wondrous exception. Coconut oil is similar to butter in that it is solid when cold, semisolid at room temperature, and liquid when heated, and so it works well in pretty much everything, from cookies and cakes to vegetable dishes. It's expensive, so try to buy it at wholesale stores or when on sale.
If you are unable to use coconut oil, keep in mind that other oils generally work best in recipes that also use liquid sweeteners, a solid fat, and some sort of emulsifying agent. Examples of such liquid sweeteners include honey, maple syrup, or molasses. Examples of solid fats include almond butter, peanut butter, or sunflower seed butter. And while eggs are really the ideal emulsifying ingredient, there's a wide range of egg substitutes as well.
If you do choose to use eggs, separating the eggs, beating the yolks with the sweetener, and then folding the egg whites into the other ingredients also helps to give your oil-based cakes and quick breads both richness and lift. This process better allows you to bake without using margarine or shortening.
It is often the case that oil-based vegan cakes that do not use eggs seem a little dense. But this problem can be remedied by combining oil with some sort of solid fat, such as ground nuts or chocolate.
Baking Cookies Without Butter
Cookies and shortbreads traditionally use butter for richness and density but rely less on butter for the lift needed in recipes like cakes. For this reason, cookies are often much easier to make dairy-free. Simply replacing the butter with margarine or vegetable shortening almost always does the trick. Using oil successfully, however, depends a good deal on the other ingredients present in the recipe. Using oil in recipes with liquid syrups and ground nuts will produce a cookie with a shortbread texture. On the other hand, using oil in combination with egg yolks and either liquid sweetener or granulated sugar will produce a soft and chewy cookie with a cakey texture. If you choose to use oil and liquid sweetener without eggs, in most cases you will either produce a thin, crisp cookie or a cookie with a muffin-top texture.
Generally, in cookie recipes and other dense, sweet dessert recipes like pie dough and cobblers, using margarine and shortening is the best choice. The exception to this rule is for baking cookies that do not use baking agents or are meant to be somewhat dense and dry.
Baking Biscuits and Pastries
For biscuits and pastries that typically use baking agents or yeast and little or no sweetener, using oil will leave the finished product lacking in both texture and flavor. These recipes are much more successful using soy margarine or shortening than anything else. Combining oil with ground nuts in biscuit or pastry recipes will not allow for the floury, breadlike texture that defines these baked goods. Furthermore, using extra eggs for richness will not allow for the desired dry texture and will produce a somewhat cakelike consistency. Really, oil does not do these products justice. This is not to say that oil cannot be used in these recipes, but the result will be vastly different from the traditional product made with soy margarine, shortening, or another semisolid fat.
Unsalted Butter vs. Margarine
Most baking recipes call for unsalted butter, and all of the soy margarine and shortenings we have come across are not unsalted. To account for this disparity, reduce the amount of salt in a given recipe by 1/4 teaspoon per 1/2 cup margarine.