How to halve baking recipes?
When scaling down (or scaling up) baking recipes, do you also halve/double/etc the baking powder/soda amount?
I want to bake this: http://smittenkitchen.com/2008/09/maj... but it calls for 3 and half cups of flour. I don't want to use anything more than 2 cups of flour, because I'll probably end up eating most of it if it doesn't turn out very good. (My cake baking skills are suspect, so far, I've only made chocolate cakes and banana cakes, and just twice at that; so I'm not exactly confident about baking cakes)
In general, when scaling recipes, what do you change and what do you not change from the original?
First of all, serious bakes don't use bulk measure; they use scaled ingredients. If you're incredibly serious about converting this recipe to about 60%, take the time to measure the ingredients as outlined in the recipe, weigh each of them (convert to grams, not ounces) and edit the data. Keep in mind that measuring flour in bulk includes the risk of error by as much as 20% compared to scaling ingredients. Check the nutritional label on your dry ingredients to determine the ratio of weight to bulk measure (it'll say something like "Serving Size 1/4 cup (30.0 g)" so one cup of the flour would weigh 120 grams) to get started.
Eh, I'll probably get yaked at for being unhelpful, but why not just bake the recipe as written with the update? It looks like an easy cake to bake, and one that would be suitable for freezing the other half. There's just a better chance it will turn out properly and if you go messing with it, you won't know if it's due to error or just a bad recipe(her recipes are great by the way).
Check out the blog Dessertfortwo.com
She scales recipes back for you, and I've had good luck with her recipes as well.
Unless I plan to modify the recipe, I scale everything.
However, as you've noticed, you don't come out with nice, even numbers if you want to scale things evenly, so I will do some rounding.
So to scale from 3.5 cups flour to 2 cups, that's multiplying by 0.57 - say 0.6.
A teaspoon comes out to 0.6 teaspoons, but that's hard to measure, so let's say a heaping half-teaspoon. A tablespoon is 3 teaspoons, so that becomes 1.8, or two scan teaspoons.
The recipe writers have adjusted the amounts so that it comes out in nice even quantities, so this approach will do very well.
What you don't want to do is use 0.6 times the amount of flour and leave everthing else the same. Too much leavener (b. powder or soda, yeast) and the baking will over-rise and possibly fall. Some types of baking will be less sensitive than others, but if the balance is off enough, the baking could fail.
This is where I like European style weight based measurements, particularly when combined with an electronic scale. I can easily scale all the weight based measurements, and liquid measurements in millilitres are much easier to scale than the cups and teaspoons.
The easiest way is to halve everything except the vanilla. You can leave that alone. If you insist on setting it up with 2 cups of flour, you will have to take everything except the vanilla and maybe the salt to 57% (ok maybe 55 - 60%) of what it used to be. Cakes are formulas. It is usually important to keep the ratios and percentages the same to duplicate the texture.