Pastry chef Camille weighs in on gougères and the milk/water issue from Paris:
I have strong opinions about the use of milk in pâte à choux. Namely, that it is not optional. In my experience, choux made with half milk is more tender, browned, and all-around appetizing than choux made with only water, which I find has a tendency to become brittle and dry very quickly. When you break down milk into its components, it looks arguably as though all those non-water parts are already in the dough somewhere else, but I think there’s more to it than that. Perhaps there’s some kind of custard action going on behind the scenes with the milk and the egg? I don’t know. While I’m as big a food science nerd as the next physical chemist’s daughter and biochemist’s wife (true story), I think that our current knowledge of these things is still limited, and calling milk a simple colloid of fats, proteins, minerals, and water is an incomplete picture. I do know you can read the labels for Plugra and Land O’ Lakes butter, and they will both say 82% fat, but that when you look at them and work with them, they behave very differently. (Given the choice, I would never make a laminated dough with anything but Plugra – or another butter that behaves the same way. I have my suspicions about Keller’s…)
And a question. Your recipe calls for AP flour. When I’ve made gougères with AP flour, they always seem to come out less airy and delicious. Pastry flour is ideal, but I’ve learned that a mixture of half cake flour and half AP works just as well. Any thoughts?
My initial thoughts on milk is that it is indeed more than the sum of its parts. It’s been closely studied, but on some level it’s still a mysterious, magic fluid. I won’t dispute that you’ve had better results with it (though I suspect it’s the extra bit of fat that’s mostly responsible for the texture difference). That proportion of pastry flour that you use would heighten then effect, I think. The decrease in protein would take away a bit of the spring, but the mouthfeel would probably be more “airy” like you describe. I’ll make these notes on the recipe. Check out Camillle’s own post on here. Thanks Camille!