So you have all the ingredients for your recipe — except one. Can you make a substitution? Frequently, yes. However, a cook must be careful about recipe substitutions. Cooking is a surprisingly complex chemistry experiment and substituted ingredients should serve the same chemical function as the omitted ingredient.
The easiest recipe substitutions regard taste. Onion powder (not onion salt) or dried onions may be substituted for raw onion in a recipe. Allspice can be used in place of cinnamon and vice versa. Cinnamon may also be combined with ground cloves and ground ginger for a more authentic allspice taste. This is true of most herbs and spices. The recipe may have a slightly different flavor than the original, but if the cook likes the spices she used, she will probably like the finished dish.
Recipe substitutions get more complicated when one is using an ingredient that has some action in the recipe, as well as adding taste. But some recipe substitutions are surprisingly simple. Out of buttermilk? Use a cup (226 grams) of plain yogurt or one cup (237 milliliters) regular milk with a tablespoon of white vinegar or lemon juice. What is buttermilk but slightly soured milk, anyway? Baking powder can also be substituted in a recipe. The formula is to use 1/4 teaspoon baking soda plus 1/2 teaspoon cream of tartar, or 1/4 teaspoon baking soda plus 1/2 cup (117 milliliters) buttermilk. When using the second option, decrease liquid in recipe by 1/2 cup. It is clear that the ingredients in recipe substitutions must always serve the same chemical function.
However, even ingredients as essential as eggs may be substituted. Try using 1/4 cup of pureed silken tofu, or 3 tablespoons mayonnaise, or half a banana mashed with 1/2 teaspoon baking powder in place of eggs. For dramatic recipe substitutions like these it may be advisable to try the recipe at home first, to see if it turns out well, before making it to take somewhere (not a bad idea for any new recipe).
Tomato sauce mixed with a little vinegar and sugar is a good substitute for ketchup, while lemon juice or white wine may be substituted for vinegar. Three tablespoons of cocoa powder and 1 tablespoon of oil substitute for one square of unsweetened baking chocolate.
Hundreds of recipe substitutions are also available on the Internet, but a cook can often think of his own recipe substitutions when considering what function the missing ingredient serves. A little ingenuity in this case may go a long way, and may even make the recipe better.