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. Doughnut shop owners I’ve met get almost mystical about it. Some have a “magic number” for their kitchens to help them keep track of temperature variations. For one doughnut maker I knew, that number was “450″. What’s that? It was his ideal oil temperature (375) plus his ideal batter temperature (75). As long as they added up to 450, he maintained, the doughnuts would be perfect. If his batter temperature was a little high, he’d lower his oil temperature by the same amount. If the batter temperature was low, he’d turn the heat up on the oil. I can’t explain why that rule seemed to work so well, it just did. Of course it varies from shop to shop, depending on the type of batter and the type of fat being used, but the principle really does seem to work. One shop owner I met added room temperature to the equation (his magic number was 520), but my brain starts to hurt when I try to consider all the possible variations.
But on to some particulars. What happens if the batter temperature is too high? The doughnut will want to spread in the oil, creating a flat ring with lots of greasy pits in the bottom. What if the batter temperature is too low? The doughnut will tend to sink, sit in the oil for too long, and soak up more fat.
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.