Makes enough to line a 25cm tart pan, or 6 10cm tartlet molds.
75g chilled unsalted butter, diced, plus a pat to grease the pan
150g plain flour
1/4 t. fine sea salt
1-2 T. cold milk
Grease a 25cm tart pan with butter.
Combine sugar, salt, and flour. Add butter cubes and rub into the dry ingredients with the tips of your fingers, until the mixture resembles coarse meal. Add a tablespoon of milk and blend it in, handling the dough as lightly as you can. The dough should still be crumbly, but should clump if you gently squeeze a handful in your hand. If it doesn't, add a little more milk, teaspoon by teaspoon, and blend again, still working lightly.
Pour the mixture into the tart pan and use the back of a tablespoon to spread it evenly over the bottom. Using the heels of your hands and your fingers, press down on the dough to form a thin layer, covering the surface of the pan and creating a rim all around. Don't worry if the dough is a little dry, this is normal. Cover with plastic wrap and refrigerate for 30 minutes or up to a day.
Variations: flavor the dough with 1 t. vanilla extract or finely grated citrus zest, 1/2 t. spice such as cinnamon or nutmeg, or 1 t. liqueur (Grand Marnier, rum). Add these ingredients along with the butter.