To shorten, in baking, is to make pastry more crumbly and tender by adding more fat. The fat shortens the gluten strands, coating flour proteins so they cannot form long, elastic networks, which is exactly what gives shortcrust and shortbread their melt-in-the-mouth texture. More fat means a shorter, more delicate crumb, but also a pastry that is harder to handle and more prone to shrinking. The balance of fat to flour defines every pastry type, from the lean toughness of a strudel dough to the rich fragility of a tart shell. It is one of baking’s fundamental levers: adjust the fat, and you rewrite the texture.