Combine flour, butter, and sugar in food processor
Pulse until mixture looks like crumbs
Add the egg and water and pulse until it forms a dough ball
Roll out pasty on a floured surface until it is a little bigger than the tart pan
Line the tin with pastry, place on a baking sheet and chill for 30 minutes
Preheat oven to 400°F
Remove the pasty from the refrigerator and line with baking parchment and baking beads
Bake in the oven for 15 minutes
Take pastry out of the oven and remove the backing beads and paper
Return the pastry to the over for another 10 minutes (or until golden brown) Set aside to cool