We are thankful to Chef Heston Blumenthal for providing this recipe from his book, Heston Blumenthal at Home.
Crisp pastry, the velvety filling, the brisk citrus sharpness as you bite in — not much beats a good lemon tart. For me the key to this tart is making the filling as smooth as possible: it has to be at the point where it’s just set and no more. If the custard is overcooked it will be too heavy and if it’s undercooked it will collapse.
Reaching that precise level of set can be tricky. In the early days at the Fat Duck I became a little obsessed with making sure that each tart we served was just right. The conventional way to check for this is the ‘Wobble Test’ — shaking the tart to see whether it’s firm enough. But how do you describe this in a recipe? The answer is a digital probe. If you use a probe to take the filling to 62oC and then 70°C (160°F), it should be spot-on.
For the pastry
- 120g Icing sugar
- 3 Large egg yolks
- 300g Plain flour
- 150g Unsalted butter
- 1/2 teaspoon Salt
- Seeds from 1/2 vanilla pod
- Zest of 1/2 lemon, finely grated
For the filling
- Finely grated zest and juice of 5 lemons
- 300g Double cream
- 390g White caster sugar
- 9 Large eggs
- 1 Large egg yolk
To finish and serve
- 80g Unrefined caster sugar
- Crème fraiche
To start the pastry, blitz together the icing sugar and egg yolks in a tall container with a hand blender.
Use a mixer fitted with a paddle attachment to mix the flour, butter and salt on low speed until it resembles fine cornmeal (approximately 2-3 minutes). Add the vanilla seeds and lemon zest, then add the egg yolk mixture 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 greaseproof paper to a thickness of 2mm, then place in the freezer for 30 minutes.
Pre-heat the oven to 180°C (355°F).
Line a 20cm tart tin (2cm deep) with the pastry (for instructions, see Heston Blumenthal at Home pp.301-3), prick the base with a fork, then place back in the freezer for 10 minutes.
Line the pastry case with scrunched greaseproof paper and beans. Place in the oven to blind-bake for 30 minutes.
After 30 minutes, remove the paper and its contents, and return the tart case to the oven for a further 10 minutes. Take the tart case out of the oven and allow to cool a little. Trim the overhanging pastry by running a sharp knife round the top of the tart tin and discard. Leave to cool completely.
When ready to bake, pre-heat the oven to 120°C (250°F), and place the baked pastry case in the oven to warm up.
Place all the filling ingredients in 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 62°C (145°F). 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 70°C (160°F). Allow to cool completely at room temperature.
Just before serving, sprinkle a thin layer of sugar on top of the tart. Using a blow-torch, gently caramelize the sugar while continuing to sprinkle further sugar on top. Serve with crème fraiche.