This week's TWD recipe inspired me to try some variations.
Since I studied science in college, and have a number of scientists and engineers in my ancestry, I decided to do some science experiments with these sablés. What would happen if I varied just one ingredient? Such as the type of flour, or sugar, or egg?
First experiment: type of flour. What happens if you use flour with a different protein content? I made one half-batch with unbleached all-purpose flour and one with unbleached pastry flour, measuring the flour by weight. Both were lemon-flavored and shaped into logs.
The ones with the yellow dot on top were the pastry flour ones. (The dot was made with egg, water and food coloring beaten together).
Results: unfortunately I underbaked the all-purpose flour batch a bit. This made comparing the two more difficult. Drat. Next time, I must remember to bake some of each batch at once. Because of the underbaking, the all-purpose flour ones were a bit doughy in the center. But by tasting just around the edges, I could make a pretty good comparison. The pastry flour ones were just a tiny bit more tender, the all-purpose flour ones were just a tad more chewy. But the difference was very slight and both were good. I also noticed that the pastry flour ones spread a bit more. This might be because lower-protein flour absorbs a bit less water, making the dough slightly more moist.
Second experiment: type of egg. I made two half-batches, one using an egg yolk (19 grams), one using one-half a whole egg (25 grams). Both were lime-flavored and used my standard "pastry and tender cookie" mixture of half all-purpose flour and half pastry flour. (I used the zest of one small lime for each half-batch.)
Results: The ones with the green dot were the whole-egg batch. There was a definite visual difference here -- the whole-egg ones were a stickier dough, spread more, and had a more open texture. The little rectangles were actually the same size and shape before baking. Part of this difference might have been because of the extra 6 grams of liquid egg; some was probably due to the difference in fat and emulsifier content. (Egg yolks have more fat and more natural emulsifiers.) Taste tests showed the whole-egg cookies were more crisp and light, while the egg-yolk ones were more smooth, rich and suave, but still "sandy". The taste difference was small but the texture difference was quite noticeable.
Third experiment: type of sugar. I made one half-batch with the mixture of granulated sugar and confectioners' sugar that Dorie recommends, and another using an equal weight of all superfine sugar. These were unflavored. Both batches were made with blended all-purpose/pastry flour, and with 20 grams of whole egg.
Results: Well, I forgot to label the rolls! I guess I was running out of energy at that point. So I don't know if the green cookies or the red cookies have the original sugar mixture. Sigh. Reducing the whole egg to 20 grams did solve the problem of the really sticky dough, but both batches still spread more and had a more crisp, open texture than the egg yolk ones. But the good news was, I couldn't tell any difference between the red and green ones. The textures were the same.
1) Unbleached all-purpose flour vs. unbleached pastry-flour -- the difference is barely noticeable.
2) Egg yolks vs. whole eggs -- the difference is noticeable. Just egg yolks give a cookie that spreads less with a more firm, even, but still "sandy" texture. The egg whites in the whole egg make for a crisper, more open-textured dough that spreads more. These things are always a matter of taste, and I liked them both. I have a feeling the egg yolk ones are more authentic, but personally I liked the crisp texture of the whole-egg ones. Just be sure to use the same amount of egg by weight or volume - about 38-40 grams for a whole recipe.
3) I couldn't tell the difference between the mixed-sugar batch and the superfine sugar batch. So, take your pick. It's easy to make your own superfine sugar by grinding regular sugar in a food processor. It would be interesting to compare a batch with all granulated sugar and all confectioners' sugar -- I'm sure that would make a difference.
And hey, what about comparing different regular butter to cultured butter to high-fat Euro-style butter? These cookies are so simple that they really reveal the differences in ingredients.
Other thoughts -- I would like these a just bit less sweet. I'm going to reduce the total amount of sugar down to about half the weight of the butter -- say, 100-110 grams for a whole batch. That's just a matter of my personal preference. I've made shortbread this way and the sweetness level was just right for my taste.
Also, the lemon and lime flavors were pretty subtle. I might increase the amount of zest next time -- I like my citrus cookies zingy!