Getting the batter just right makes all the difference when it comes to deep-frying fish or chicken. Too thick and it's like biting into nothing but fried flour, but too thin and it falls apart in the hot oil. Deep-frying batters typically include flour, a liquid and a leavening agent to fluff up the batter. While fish benefits from a light batter that won't overpower the delicate flavors, chicken can handle a thicker batter that gives it a hearty crunch. Start with the same basic batter for both, adjusting the ingredients to suite the meat of your choice.
Add a low-protein flour, such as cake or corn flour, to a large mixing bowl. Low-protein flours don't have as much gluten, which keeps the batter crisp for longer after frying. You can also use gluten-free flours such as rice flour.
Season the flour to your liking. Depending on the flavor you are going for, you can add dry seasonings such as salt, black pepper, paprika, garlic powder, onion powder and cayenne pepper.
Pour a liquid into the seasoned flour to create the batter. Add liquid equal to the amount of flour for a slightly thick batter. While you can use water, adding milk or beer for the liquid creates a richer flavor. Beer also adds carbon dioxide and foaming agents, which help create a light and crisp crust. Adjust the liquid amount as needed for a thin or thick batter.
Add a leavening agent to the batter, which will aerate and lighten the batter. Leavening agents you can use include baking powder, baking soda or beaten egg whites. Beer also acts as a leavening agent. Add roughly 1 teaspoon of baking soda or baking powder or 1 beaten egg for every 1 cup of flour.
Chill the batter for 20 minutes in the refrigerator before using. Chilling the batter helps it adhere to the meat better. Batter containing baking powder should be chilled only briefly, because it loses its leavening power quickly and must be cooked as soon as possible.