Cutting in shortening is a crucial step in many baking recipes, especially pie dough - it's the technique that helps ensure flakiness. Cutting in is easy, but some ways are better than others.
Make sure the shortening is chilled but not too cold. You should be able to mold it with your fingers.
Mix the dry ingredients, including flour, according to your recipe.
Cut the shortening into large chunks.
Add the shortening all at once to the dry ingredients.
Mix the shortening with your fingers so that each piece gets coated with dry ingredients.
Scoop up some of the coated pieces and loose flour. Rub the shortening pieces through your fingers, breaking them into smaller pieces.
Repeat step 6 until the mixture is loose and crumbly and resembles coarse meal. Different-sized pieces of shortening, plus a small amount of loose flour, create the ideal texture, especially for piecrust.
Continue with your recipe.
The coarse meal appearance is key to this technique. When pressed together and rolled flat, the pieces of shortening will eventually become individual flakes in the finished crust (or biscuit, or what have you).
It's important that the pieces be of different sizes - from olive- to pea-sized.
You can mix in shortening with a large fork, two knives that you draw toward each other or a tool called a pastry cutter or pastry mixer. These tools work well, but the human touch yields better results.
Most people use butter, lard or solid vegetable shortening, but shortening can be any edible fat. It's called "shortening" because of what it does to the flour. When moistened and mixed, flour develops gluten, strands of protein that give baked goods their structure. When fat is cut in, it shortens the gluten strands, making the food more crumbly, hence the name.