Creaming Butter or Margarine If the butter isn't soft enough it won't mix completely with the sugar and you will get lumps of fat that will “fry” your cake and although still tasty it is difficult to decorate and ice the cake and it will look oily.
Your eggs or milk are too cold!
The blobs in the batter are pieces of butter. This butter breaks out of the batter when the fat gets too cold and seizes. It's important that all fat and dairy, including butter and eggs, should be brought to room temperature before you use them in batter.
Floury Lumps
If you have already added the flour and are left with a lumpy cake batter, don't worry. Just use a whisk or electric mixer and mix on low speed until the lumps have disappeared. Just make sure you don't overmix your cake batter or you'll end up with a dense cake.
A good rule of thumb is to mix ingredients until just combined; the combined batter for spongy cake mixes should look satiny and form peaks, while an undermixed cake batter may have visible flour streaks and a chunky appearance. On the other hand, an overmixed batter will likely become runny and slack in appearance.
Over-creamed butter and sugar adds in too much air and alters the final texture – typically to be more gummy and dense. Sometimes over-creaming can produce cakes, cupcakes, or cookies that collapse upon baking or while cooling if the mixture is well and truly over-creamed (where it looks like curdled milk).
Cold eggs – when you add cold eggs to your sugar butter mixture at room temperature it brings down the overall temperature of the batter. This causes it to break because the fat turns cold and solidifies. When butter solidifies, you'll see small chunks of butter in your batter.
Butter that is too cold won't expand very easily and it'll never capture much air. The result? Heavy and dense, the creamed butter will resemble chunky, grainy spread the consistency of natural peanut butter.
Lumps are actually okay! Stir your batter until the dry and wet ingredients are just incorporated. That means mixing until the flour streaks have disappeared, but leaving the pesky lumps. If you over-mix, the gluten will develop from the flour in your batter, making your pancakes chewy instead of fluffy.
Plus, it's really easy to make them from scratch, with results that are many times better. But one of our test cooks discovered the key to perfect pancakes is lumpy batter. You may have heard that overmixing pancake batter can cause gluten to develop, which in turn gives you a dense pancake.
Furthermore, if the eggs are too cold, it is highly likely that when you add them to the creamed butter and sugar, the butter will harden and form lumps. Either way, what this means is the batter is uneven, and the crumb/air bubbles in the baked cake will be too.
However, at a certain point, you might increase the amount of butter so much that the cake starts becoming dense again and begin to fall into itself—eventually getting closer to the texture of a greasy brownie instead. Also, increasing butter tends to decrease the sweetness of the cake.
Melted or liquid butter will thin out your batter, giving you ultra-flat cookies or cakes that are dense and uneven.
Butter that is too warm won't aerate properly when beaten with sugar, leading to a decidedly un-fluffy result. As a general rule, whenever a recipe starts with creaming butter and sugar, it's a good idea to really let your butter reach room temperature so the final result has the optimal texture.
Making pancake and waffle batter ahead of time is a huge no-no and will lead to flat, dense results every time. Even letting your batter hang out for just a few minutes after you've mixed it before you start ladling it onto the griddle will lead to less fluffy results.
The eggs are too cold. If eggs are colder that the temperature of the butter mixture when added, they can cool the butter down and cause it to become more solid. This will have the same effect on the emulsion as if the eggs are added too quickly and will also cause the emulsion to split.
Thick Batter. It is generally believed that thick batter results in a dense and stiff cake that will dry out easily. While this is true in some cases, some cake batter is naturally thicker and the adequate thickness of the batter results in a light and fluffy cake with tight crumbs.
If creamed too long the mixture will turn white and, if you use it, will give your baked goods a dense, almost gluey, texture. So, don't leave your mixer unattended and keep an eye on the mixture so you can see when it's ready. Unfortunately, there isn't a way to correct over-creamed butter and sugar. What is this?
Increase speed to medium-high and beat butter and sugar for 1-2 minutes, or until mixture is smooth, has lightened in color, and has significantly increased in volume. For best results, scrape down the sides and bottom of the bowl with a spatula at least once or twice before the creaming process is complete.