Shortcrust is flour, fat, salt and just enough water to hold it together. Everything that goes wrong with it comes down to two things: the fat got warm, or the dough got too much water and too much handling.
The ratio
Half fat to flour by weight is the classic: 250g flour, 125g cold butter, a good pinch of salt, and roughly 2 to 3 tablespoons of very cold water. For a sweet crust, add a tablespoon of sugar and use one egg yolk as part of the liquid.
All butter tastes best. A mix of butter and lard or shortening is more forgiving and gives a shorter, more crumbly texture. Both are correct; pick the one you want to eat.
Keep everything cold
Cold butter in flour stays in small pieces. Those pieces melt in the oven and leave layers and air. Warm butter smears into the flour, coats it, and gives you something closer to a biscuit.
Cube the butter straight from the fridge. If your kitchen is warm, put the flour in the fridge too, and use a food processor in short pulses rather than warm hands. Stop when the mixture looks like coarse breadcrumbs with some pieces the size of peas still visible. Those pieces are the point.
Water: less than you think
Add the water a spoonful at a time and stop while the mix still looks too dry. Press a handful together: if it holds, it is done. Too much water develops gluten, which makes pastry tough and makes it shrink in the tin.
Bring it together with a knife or your fingertips, not by kneading. A finished shortcrust should look slightly marbled, not smooth.
Rest it twice
Flatten the dough into a disc, wrap it and rest it in the fridge for at least half an hour. This lets the flour hydrate evenly and relaxes the gluten you did develop.
Then, after you have lined the tin, chill it again for twenty minutes before baking. This second rest is the single best defence against shrinking sides. Pastry shrinks because the gluten pulls back as it heats; cold, rested dough pulls back much less.
Rolling
Roll on a lightly floured surface, turning a quarter turn between passes so it stays round and does not stick. Roll from the middle outwards rather than back and forth across the whole disc.
To move it, roll it loosely around the pin and unroll it over the tin. Ease it into the corners instead of stretching it; stretched pastry shrinks back in the oven every time. Leave the overhang until after baking, then trim it with a knife for a clean edge.
Blind baking
A wet filling in raw pastry gives a soggy base. So bake the case first: line it with baking paper, fill it with beans or rice, and bake at 190°C for about 15 minutes, until the sides are set and dry-looking. Remove the paper and beans and bake another 5 to 10 minutes until the base is pale gold.
For a very wet filling, brush the hot base with beaten egg and give it two more minutes. That seals the surface, and it works.
When it goes wrong
- Cracks when rolling: too dry, or too cold. Let it sit five minutes and patch cracks with offcuts; nobody will know.
- Sticky and impossible: too warm. Back in the fridge for twenty minutes rather than more flour.
- Shrunken sides: stretched dough, or not chilled before baking.
- Tough: too much water or too much working. Next time stop earlier.
- Soggy bottom: not blind baked, or the tin was glass or ceramic; metal conducts heat far better.
Offcuts, incidentally, are the best part. Roll them out, sprinkle with sugar and cinnamon, bake for ten minutes and eat them standing at the counter while the pie cools.