Vanilla Bean Petticoat Tails

Method

1. Split the vanilla pod lengthways, scrape out the seeds with the back of a knife and rub them into the sugar with your fingertips to perfume it. The butter should be about 18 °C: it bends without breaking but is not greasy. Beat the butter, vanilla sugar and salt with a spatula for 2 min, just until smooth, without whipping in air.

   Add in this stepBest-quality unsalted butter, at about 18 °C 80 gCaster sugar 40 gVanilla pod ½Flaky sea salt 1 pinch

2. Sift the flour and rice flour together twice, then add them. Cut them in with the spatula until crumbly, then press lightly with your hand into one dough. Stopping just before the dough looks smooth is the secret to a short, sandy crumb.

   Add in this stepPlain flour 100 gRice flour 30 g

3. Set a 17 cm ring or tart tin (or a circle drawn to that size) on baking paper and press the dough in evenly 1.2 cm thick. Remove the ring and crimp the edge between thumb and finger. Stamp a 3 cm circle in the centre, score 8 wedges per round halfway through, and prick with a fork. Scatter over half the demerara, press it in lightly, and chill for 30 min until firm.

   Add in this stepDemerara sugar 4 g

4. While it chills, preheat the oven to 150 °C (130 °C fan). Baking lower than usual keeps the colour pale and crisps the shortbread evenly right through.

   oven

5. Slide the dough on its paper onto a tray and bake in the oven for 40 min, until the edges are barely pale gold and the top is cream-coloured. Sprinkle the rest of the demerara over as soon as it comes out.

   Add in this stepDemerara sugar 4 g

   oven

6. While hot, cut through the score lines again and cut out the centre circle. Cool on the tray for 20 min, then move to a rack to cool completely. A day in an airtight tin lets the butter and vanilla flavours mellow together.