Heston's definitive lemon tart recipe is made from rich lemony pastry filled with zesty lemon custard
Heston: "For this tart to achieve greatness, the filling has to be exactly the right texture – not too soft but not too firm either. The most reliable way to get it right is to use a digital probe which takes out all the guesswork. When blind baking, the pastry should be treated like a biscuit; if you think it is done, cook it for a little bit longer. Also, use the best lemons you can so that they contribute great acidity."
For the pastry
For the filling
Using a mixer fitted with a paddle attachment, mix the flour, butter and salt on low speed until it becomes a sand like texture (approximately 2-3 minutes).
In the meantime, in a tall container blitz together the icing sugar and egg yolks with a hand blender.
Add the vanilla seeds and lemon zest to the egg yolk mixture and then add to the bowl in the mixer and continue to mix on low speed until fully combined and a very soft dough has formed (approximately 3-5 minutes).
Mould the dough into a flat rectangle and wrap it in clingfilm before placing in the fridge for at least 1 hour.
Roll the pastry between two sheets of baking paper to a thickness of 2mm, using two stacked 2 pence coins as guides, then place in the freezer for 30 minutes.
Pre-heat the oven to 190ºC/gas mark 5. Line a 26cm tart tin (2.5cm deep) with the pastry making sure to press it into the edges and leaving the pastry hanging over the edge.
Take a sheet of baking paper and scrunch it up several times to eliminate any sharp edges. Prick the dough with a fork all over the surface. Place the baking paper on top and add enough coins (or baking beans) to fill the casing ¼ of the way up. Place in the preheated oven to bake for approximately 20 minutes or until fully cooked.
In the meantime, mix some of the leftover dough with an egg using a hand blender.
After 20 minutes, remove the baking paper and coins and, using a pastry brush, brush the entire surface of the tart with the dough and egg mixture. This ‘liquid pastry’ will ensure that any holes will be sealed. Return the tart to the oven for an additional 10 minutes.
Remove the tart from the oven and allow to cool completely.
When ready to bake, preheat the oven to 120ºC/gas mark ½. Place the baked pastry case in the oven to warm up.
Put all the filling ingredients into a bowl and mix together using a spatula. Place the bowl over a saucepan of simmering water and allow to warm up until the temperature reaches 60ºC. At this point, strain the mixture through a fine sieve into a jug. With a spoon, remove the bubbles from the surface of the liquid.
Slide the oven rack out a bit, then pour the mixture into the warm pastry case inside the oven. Fill the case to the top, slide the rack carefully back in, and bake the tart for approximately 25 minutes or until the temperature of the filling reaches 70ºC. Allow to cool completely at room temperature.
Just before serving, trim the overhanging pastry by running a sharp knife round the top of the tart tin and discard.
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