Cocoa powder gives a recipe an intense chocolate flavour, and it also significantly darkens the final product. Cocoa also dries out and stiffens baked goods, so recipes using cocoa usually require extra fats. The cocoa's exact flavour contribution depends on the type of cocoa called for in your recipe. Natural and Dutch-processed cocoa are unsweetened, but Dutch-processed cocoa is less bitter than natural cocoa powder because it has added alkali. Most recipes use natural cocoa, and these recipes often also call for baking soda that reacts with the acidic natural cocoa. If you're out of cocoa, you can use semi-sweet chocolate chips instead.
Rewrite the recipe on another sheet of paper. For every 6 tablespoons of cocoa your recipe calls for, use 170gr of semi-sweet chocolate chips. For example, if your recipe calls for 3/4 cup cocoa, which is 12 tablespoons, add 340gr of semi-sweet chocolate chips to your ingredients list. Replace all the references to cocoa in your recipe with semi-sweet chocolate chips.
Reduce the sugar in the recipe by 7 tablespoons for every 170gr of chocolate chips you add to the recipe. Since the chocolate chips are more sweet than the cocoa, your recipe requires less sugar.
Reduce the butter or other fats in the recipe by 1/4 cup for every 170gr of semi-sweet chocolate chips. Chocolate chips already contain fat and won't dry or stiffen the recipe as cocoa would.
Add 1/8 teaspoon baking soda for every ounce of chocolate chips you add only if you are substituting for Dutch-processed cocoa in your recipe.
Chop the chocolate chips to a fine consistency and add them to a plastic bowl. Microwave the chopped chips in 10- to 15-second increments. After each increment, check the chips for softness and stir them together. Once the chocolate is liquefied, it's ready to use in your recipe.
Remember that there are 16 tablespoons in 1 cup and 3 teaspoons in 1 tablespoon.