Make Pastry Mixture: In a high-speed food processor, add flour and powdered sugar. Pulse a couple of times to blend. If you don't have a food processor, see notes for an alternative method.
Blend Butter: Add the chilled cubed butter and pulse for 15 seconds until the mixture resembles coarse crumbs.
Add Water: Through the vertical shoot, drizzle a tablespoon at a time of the chilled water while pulsing the mixture until it forms a rough dough. If the dough is too dry, add a little more water until it sticks together.
Knead Dough: Transfer the dough onto a lightly floured surface. Gently knead into a smooth ball, being careful not to over-knead.
Chill Dough: Flatten the dough into a thick disc and wrap it in plastic cling film. Refrigerate for 15 minutes.
Prepare for Baking: Preheat the oven to 350ºF (180ºC). Generously grease two 12-hole shallow tart pans (patty pans) with butter. Set aside.
Roll Dough: Remove the dough from the refrigerator and roll it out on a lightly floured surface into a large circle measuring 4mm-5mm in thickness and about 35cm / 14 inches across.
Cut Rounds: Using a 6cm/2.4 inch round fluted cookie cutter, cut out the bases.
Shape Tarts: Place them gently into the greased patty pans. Lightly press the dough into the shallow wells.
Re-roll and Cut: Repeat with the remaining dough, re-rolling any scraps to make more bases. This recipe makes 24-28 bases.
Fill Tarts: Spoon 2 level teaspoons of jam into each crust, being careful not to overfill to prevent boiling over during baking.
Bake: Bake for 15-20 minutes or until the pastry edges look cooked and are pale to very lightly golden in colour. It's okay if some parts of the crust appear paler.
Cool: Allow to cool in the pan for 10 minutes before removing.
Remove from Pan: Carefully slide the tarts out from the pan with a butter knife and transfer them to a wire rack to cool completely. They will firm up as they cool. Enjoy!