To make the pastry, dice the butter, then pulse with the flour in a food processor until the mixture resembles fine breadcrumbs.
Add the sour cream and continue to pulse until the dough starts to incorporate into a ball.
Wrap the dough in plastic film and refrigerate for 20 minutes.
Roll the chilled pastry out to 5mm thickness and carefully line tart tin. If blind baking for a tart, gently press the pastry into the edges and trim off the excess pastry 2cm above the top of the tin, this will allow for shrinkage.
Line the pastry with baking paper and fill with baking beads.
Place into the preheated oven 220 degrees and bake for 15 minutes, then remove the baking beads and baking paper and continue to bake for another 10 minutes. Remove and set aside to cool, ready for your filling.
