Vegan lemon meringue pie

Tip the flour and butter into a mixing bowl and mash together with a cold metal whisk until it's the consistency of breadcrumbs – you can use your hands, but your body heat might start to melt the butter. Add the sugar, ½ tsp of salt and 2-3 tbsp of ice-cold water, gradually adding enough water to bind the mixture. Knead until you have a smooth ball of dough, then wrap and chill for 20 minutes. Butter a 25cm tart tin and dust with flour, shaking off the excess.

Roll the pastry out on a floured worksurface until about 3mm thick. It can be useful to place baking paper over the pastry as you roll it to stop it sticking or tearing. Roll the pastry around the rolling pin and drape over the prepared tin. Delicately push the pastry into the edge of the tin, then trim the excess. Prick holes in the bottom of the pastry with a fork and chill for another 20 minutes. Heat the oven to 180C/fan 160C/gas 4.

Line the case with a scrunched-up piece of non-stick baking paper and baking beans, uncooked pulses or rice. Bake for 20 minutes, then remove the beans and paper and bake for 25 minutes more until golden. Cool while you make the pie filling and meringue.

To make the filling, mix the cornflour and milk together in a bowl. Heat the rest of the ingredients together in a pan over a low heat until warm and combined, then add the cornflour mixture. Turn the heat to medium-high and cook, whisking often until the mixture is thick and bubbles slowly – it's essential for the lemon curd to reach boiling point to activate the agar agar. Remove from the heat and pour the filling into the cooled pie crust. Cool for 2 hours at room temperature.

To make the meringue, heat the aquafaba in a pan over a low heat for 15 minutes until reduced to 150ml. It can be useful to weigh the liquid after 12 minutes to see how far you have to go. Cool for at least 1 hour.

Pour the cooled aquafaba into the bowl of a stand mixer with the cream of tartar. Mix at medium-low speed for 10-15 minutes until soft peaks form. Meanwhile, bring the caster sugar, agar agar and 80ml water to the boil in a small pan, resisting the urge to stir it. When the mixture reaches 121C on a sugar thermometer, remove from the heat and slowly pour it down the inside of the stand mixer bowl into the aquafaba meringue.

Mix for a couple of minutes more until the meringue is glossy and thick. Spoon it over the pie filling and leave to cool for 20 minutes. Softly brown the meringue with a kitchen blowtorch or flash it under a hot grill. Chill briefly, then serve.