Pâte sablée
Pâte sablée is a short, crumbly pastry of flour, butter, icing sugar and egg. The name comes from the French sable, "sand", and describes the baked texture exactly: it crumbles rather than snaps.
The shortness comes from fat coating the flour particles and obstructing gluten development. Two rules follow: keep the butter cold, and mix only until it comes together. Any extra mixing makes the dough elastic, and it will bake tough and shrink in the tin.
Sablée is distinguished from its relatives. Pâte brisée has less sugar and no egg, is more neutral and goes under savoury fillings. Pâte sucrée carries more sugar and bakes denser and crisper, closer to a biscuit.
The finished dough is chilled before rolling and chilled again once lined into the tin — cold dough shrinks less in the oven. For tarts the case is usually blind-baked under weights.