Step 1 of 4

Press and bake the base

Heat the oven to 350°F and line a 20 by 20cm pan, leaving overhang. Rub the cold butter into the flour and powdered sugar until it clumps, press it firmly into the pan and bake for 22 to 25 minutes until pale gold all over.

— Bake it until it is properly colored, not just set. This layer has a wet custard poured onto it and a pale, underbaked base turns to paste.