The next step is to pre-bake the tarts. We use 120mm baking trays of anodised aluminium with a loose bottom. Butter the trays, and roll out the dough to an even thickness of 3mm. Line the trays with the rolled-out dough. Be careful to tuck it into the corners but not to stretch it too thinly as you do so. Cover each tarte with greaseproof paper and a handful of pie weights.
Pre-heat the oven to 190C, then bake the tarts until they begin to turn golden at the edges (12..15 minutes).
Remove from the oven and remove the covering paper and pie weights immediately, but keep them in the baking trays.
Reduce the heat to 180C and keep the oven hot for the final bake.