Cake doughnuts, especially when they’re made from scratch, are extremely fussy things. I can’t emphasize enough how important temperature is to getting them just right. The most common problem with cake doughnuts is an too-high batter temperature. When the temperature of the batter goes up (usually because the temperature of the room goes up) the fat in the batter softens or even melts. This causes the batter to get runnier than it would ordinarily be, and that causes a couple of problems. First, because the batter falls through the depositor incorrectly — and then spreads out in the oil — it creates a doughnut with a lower volume. Second, because the batter is more porous, it creates a greasy doughnut. So if your room is hot and your doughnuts are turning out thin and greasy, try switching to shortening instead of butter as your batter fat since it has a higher melt point. You can also simply try to firm up your batter by reducing the amount of fat and/or increasing the amount of flour.
Sometimes the reverse happens and the batter temperature is too low. In that case the batter will be firmer than normal and again won’t fall through the depositor. The resulting doughnut will have a lower volume and may again be greasy as it will tend to sink and sit in the oil for too long and soak up too much fat. The solution is to simply let the batter sit until it warms up.
What about the oil? If the oil temperature is too high, the doughnuts will turn out small and fat. The reason, because the outside skin of the doughnut will harden before the interior gets a chance to rise. The result can be a virtual tennis ball. If the oil temperature is too low, once again the batter will want to spread out into very large, flat rings (that turn out very, very greasy).
So you see there are a lot of things to consider if you want a perfect doughnut. How obsessive you get about them is up to you, but I’ll tell you right now you’ll need a good thermometer. How obsessive am I about my doughnuts? Just ask the missus. That, however, is no reason for you to get uptight. As you can see from the below recipe, decent doughnuts are very easy things to mix and to make. Push the perfection envelope as far as you like, but above all have a good (safe) time. Even an imperfect doughnut is one fantastic breakfast.