Heston Blumenthal’s How to Cook Like Heston covers a different main ingredient each week. Just as in my last post, I’ve made another egg dish – the Lemon Tart from the show. This one is a bit tricky in that you have to cook it just perfect to ensure that the egg are cooked enough, but don’t become “eggy”. This recipe calls for a little vanilla and lemon in the crust, which is pre-baked before you add the custard. Then using precise and periodic internal temperature readings will get you the perfectly set custard for your tart. This one was a fun one. I used Heston’s method of evening out the crust cooking – using coins instead of beans as weights which finally gave purpose to my little collection of foreign coins. I didn’t roll out the dough thin enough and as a result, I had leftover custard, which I just went ahead and cooked in a stove pan anyways.
Heston’s recipe is here, but I’ve reprinted it for you below, with conversions from metric, however, keep in mind that metric is much more precise!
 couple of notes, thanks to my good friend, Susanna, who pointed out that Americans might not understand a few terms: caster sugar is superfine sugar and icing sugar is confectioners sugar in The States. Double cream may be hard to find – it is 48% butterfat, but you can just use heavy whipping cream as a substitute.
For the pastry
300g plain flour (2 1/2 cups)
150g unsalted butter (1/2 cup + 2 tbsp OR 10 tbsp or 1 stick + 2 tbsp)
½ tsp salt
120g icing sugar (1 cup + 3 tbsp)
3 large egg yolks
Seeds from ½ vanilla pod
Finely grated zest of ½ lemon
1 egg for the egg wash
For the filling
Finely grated zest and juice of 5 lemons
300ml double cream (1 1/4 cups)
390g white caster sugar (1 3/4 cup + 2 tbsp)
9 large eggs
1 large egg yolk
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.