Cut the butter into small cubes and freeze for at least 30 minutes
Put the flour in the bowl of a food processor and sprinkle the butter over it.
Process for two or three pulses until the mixture is like sand.
Add 1-2 tablespoons whole milk and pulse for 7 seconds. Test the dough by pinching it between your fingers. It should hold together. Add a little more milk and repeat the process until it does.
Turn the pastry dough out onto a clean board and knead until it forms a pliable dough.
Separate into two equal balls and flatten each one into a thick disk.