If you've mistakenly left out baking soda or baking powder from your wet cake batter and you want to incorporate it after the fact, there's still a way to do it. While it's not ideal and may not yield the exact same results as if the leavening agent was added initially, you can follow these steps to try to distribute it as evenly as possible:
Dissolve the Baking Soda/Powder: If you are using baking soda, dissolve it in a small amount of warm water. For baking powder, you don't need to dissolve it. Dissolving baking soda in water helps to evenly distribute it throughout the batter.
Mix Gradually: Add the dissolved baking soda or baking powder to the wet cake batter gradually. Pour a small amount at a time and mix thoroughly with a spatula or whisk.
Avoid Overmixing: Mix the batter gently to avoid overworking it. Overmixing can lead to the cake becoming tough and may not yield the desired texture.
Bake Quickly: Once you've incorporated the leavening agent, try to get the batter into the oven as soon as possible. Baking soda and baking powder begin to activate once they come into contact with liquids, so the sooner you bake the cake, the better chance you have of getting some leavening action.
Use a Quick Baking Method: If possible, choose a baking method that allows for a quick rise in the oven. For example, you can make cupcakes or smaller cakes instead of a large cake, as they tend to rise faster.
Avoid Opening the Oven: While the cake is baking, avoid opening the oven door frequently. The temperature fluctuations can affect the rising process.
Keep in mind that adding the leavening agent after the initial mixing might not result in the same level of leavening and may affect the texture and rise of the cake. The cake might be denser and not rise as much as it would have with the baking soda or baking powder correctly added from the beginning.
In the future, to prevent such mistakes, it's helpful to gather and measure all your ingredients before starting the recipe. This way, you can ensure that all the necessary ingredients, including leavening agents, are included in your cake batter.