Generally, shortcrust pastry benefits from minimal handling; aim for just enough folds to bring the dough together, typically one or two folds after the initial mixing. Overworking the dough develops gluten, leading to a tough pastry.
The key to a tender shortcrust pastry lies in preventing gluten development. Gluten forms when flour proteins are hydrated and agitated. Therefore, the less you handle the dough, the more delicate your pastry will be. After mixing the ingredients (flour, fat, water, and sometimes sugar and salt), the dough will likely be crumbly. Gently bring the dough together on a lightly floured surface. You might need to gently press it into a disc. Then, give it one or two folds. A fold involves flattening the disc slightly, folding it in half or thirds, and then gently pressing it down again. These folds help to distribute the fat evenly throughout the dough, creating flaky layers. Avoid kneading or excessive handling. Wrap the dough in plastic wrap and chill it for at least 30 minutes before rolling it out. This chilling period allows the gluten to relax and the fat to solidify, further preventing a tough pastry.
Use ice-cold water when making shortcrust pastry. The cold temperature helps to keep the fat solid, which is crucial for creating flaky layers. If the fat melts too quickly, it will incorporate into the flour, leading to a tough and greasy pastry.