Based on what I posted just below, you can see that there’s not terribly much to a biscuit. Sift, mix, pat, cut, bake — you’re outta there. Yet that simplicity belies a rather complex mechanism, one which if not treated just so will malfunction to the disappointment of all.
It’s true that the biscuit is the archetypal chemically-raised foodstuff. Yet like all baked goods, it relies heavily on mechanical leavening to reach its full potential. For the dough of a biscuit (if mixed properly) contains large pockets of butter, which in the shaping and cutting process are patted down until they become more or less flat. Once in the oven, those rough layers of butter melt, creating spaces that fill first with CO2, then steam which ultimately pushes the biscuit up. In this way biscuits are actually quite similar to laminated pastry, which is why it’s important during the mixing and shaping phase to work quickly and keep the dough as cool as possible.
An interesting feature of good biscuits is that they contain virtually no activated gluten. This is as much a factor of the speed at which they’re made as it is the fact that they aren’t kneaded. For gluten molecules will indeed find a way to hook up with one another in a moist environment, even if they’re simply left to sit (remember that this is how the New York Times famous “no-knead” bread works). By hurrying the process along, you severely limit the time they have to connect.
The upshot is of course a very tender biscuit, one without a springy gluten mesh “structure” to trap and hold gas bubbles — or constrain its explosive, willy-nilly rise. The funny thing about a “chemically raised” biscuit is, most of the CO2 that the baking powder gives off in the oven simply leaks right out the top and sides. Yet enough collects within those butter layers that the overall effect is like a bottle rocket pushing that loosely constructed, fat-laden dough up, up, up.