Pick Your Powder

• Before you start, it's important to understand that protein powders come from a range of sources, and the various kinds will perform differently in baked goods. Dairy-based whey protein performs well, but tends to dry out your baked goods unless you add moisture. The same is true of casein, another milk-derived protein, which lends a rich flavor to cookies. Egg-white powder is often problematic in cookies, leaving them with a rubbery texture and "eggy" flavor. Pea-based powder works well in cookie baking, giving your finished cookies a pleasantly friable texture that's similar to conventional cookies. Other plant-based protein powders, including rice powder, soybean powder and hemp powder, are also well suited for cookie baking.

Easing Your Way In

• If your goal is simply to bake conventional cookies with improved protein content, the differences between the protein powders will play a relatively small role. Start by removing 2 to 3 tablespoons of flour from each cup your recipe calls for, and replacing them with your protein powder of choice. In most cases, your cookies will be largely unchanged, depending on the protein you're using. Bake one or two test cookies first, to make sure they're not coming out drier than they should. If they are, add a splash of milk or fruit puree for moisture -- and try again.

Protein-Heavy Cookies

• If you're aiming for a serious high-protein cookie, either as a post-workout snack or as a low-carb treat, things are different. You're more likely to have success with a recipe that's built around protein powder -- especially a specific protein powder -- until you get a feel for how it performs as an ingredient. Don't try to change things up until you've made the recipe a few times. It's especially important not to cut back on fat-rich ingredients, such as nut butters, which counter the tendency of most protein powders to make the cookies dry and rubbery.

A Few Key Pointers

• Protein-heavy cookies tend to be somewhat harder than conventional cookies, so err on the side of underbaking. Your cookies should still be a bit soft in the middle when you take them out. They might be slightly denser than regular cookies, but should still be palatable if your recipe is good. When you feel confident enough to begin making up or evolving your own recipes, pay close attention to how others are constructed. You can vary the ingredients widely, but the ratios of protein powder to sugar, nut butter and other ingredients should remain fairly constant overall.