Whether you’re making pie crusts, biscuits, or shortcakes, one of the first steps is to cut the fat into the flour—a shorthand way of telling you to break the fat into small pieces and coat them with flour. How much you cut in the fat affects the texture of the final pastry, and to a lesser extent, so does the tool you use.
The more thoroughly you cut in the fat, the more you “shorten” the dough, and the more homogenous, crumbly, and shortbread-like it will be. Recipes that say to cut in until the dough resembles coarse cornmeal are going for a tender result. For pie crusts and biscuits that are meant to be flaky, the recipe should tell you to leave some of the fat in pea-size pieces, with the rest in crumb-like bits to ensure some tenderness. (If the pieces of fat are too big, you’ll get gaping holes in the pastry where the fat was.)
Start with well-chilled fat and work quickly. In hot weather, chill the flour and the bowl, too. Start with mini pats of butter (cut a stick lengthwise into quarters and then into thin pats) or small chunks of shortening, lard, orsuet, and toss them in the flour, distributing them evenly before cutting in.
To cut in with two knives, drag the blades through the fat until the pieces are pea-size or smaller.
Many tools, one technique. My favorite tool for cutting in is my hands. As I rub the bits of fat between my fingertips and thumbs, I control just how flaky my biscuits will be. Don’t use your palms: they’re too warm.
For large jobs, or if I’m pressed for time, I rely on a food processor fitted with the metal blade. It takes just a few short pulses to cut in the fat. Stop as soon as you have the desired texture; a few superfluous pulses will make the consistency too fine.Another efficient tool is a hand-held pastry blender with several parallel curved metal tines (rigid blades seem to work better than flexible wires). Press the tines into the fat, tossing the pieces in the flour and stopping occasionally to scrape the fat from the tines. A fork works the same way except that you need to be more careful not to smear the fat. Some pastry-supply stores sell forks with wide-spaced tines just for this purpose, but it’s difficult to get good results unless you’re very adept.
You can also cut in fat using two table knives. With a knife in each hand, drag the knife blades through the flour and fat, sliding the blades across each other to trap the fat, cutting the fat into smaller and smaller pieces.