We use Land O Lakes Salted Butter in all recipes, unless otherwise specified.
Why Land O Lakes? Because it’s widely available, and it’s always consistent. (Land O Lakes is 81% butter fat, 1.3% milk solids and 17.7% moisture.) Some bargain brands are less consistent and contain more water.
Butter (as opposed to margarine or “butter spread,” etc.) must contain 80% milk fat. Premium butter contains more, and products below 80% cannot be called butter.
It’s the amount of water you want to know about because that’s what can wreck your recipes.
A good rule of thumb to keep in mind: Lower moisture butters result in better-textured baked goods and better flavor in general. The amount of water (or moisture) in butter can make the difference between cookies that hold their shape and those that spread and burn. And because high-quality butter has less water, savory applications, like sauces, will taste better also.
Salt is used as a preservative in butter production. Although spoilage is not much of a problem today, salted butter stays fresh longer than unsalted.
Official Ingredients of the Southern Living Test Kitchens