We’ll begin with the pastry. Chop the butter into small cubes then combine with the flour in a food processor. Blitz until it resembles breadcrumbs – try not to over-blend it, or it will become too fine. Remember, with baking it’s vital that you get the exact measurements for your ingredients, so be sure to weigh the butter and flour first – why not use our stylish Swan Retro Scale
Add 1tbsp of cold water, then give it another pulse in the blender. After that, keep adding water, a little at a time, until the mixture comes together.
Once your dough is ready, spread some clingfilm on your countertop and tip the dough into the centre. Gather it up until the dough is wrapped tightly in a ball. Place in the fridge for 20 minutes.
Take the dough out of the fridge and roll it out until it’s about half a centimetre thick. Line a loose-bottomed tart tin with the dough, then put it back in the fridge for another 20 minutes. While the dough is chilling, preheat your oven to 200C / Gas mark 6.
Line the pastry case with baking paper and fill with baking beans. Bake for 20 minutes.
Remove the baking paper and beans and return to the oven for a further 10 minutes. Take your beaten egg yolk, brush it over the pastry, and bake for a final 3 minutes. Leave to one side while it cools.
In the meantime, let’s get the filling sorted. Whisk the sugar, eggs, and yolks in a heatproof bowl until they’re smooth. Combine the lemon juice and limoncello in a measuring jug. You can even grate in a little of the zest of your lemons.
On the hob, heat a pan of water until it’s simmering gently, then place the bowl with your curd mixture on top of it. Whisk until it’s slightly thickened – this should take a minute or two – and then pour in half of your liquid mixture. Keep whisking until it’s thickened up again, then add the rest. Keep whisking until it’s nice and thick.
Remove from the heat and add the butter, a little at a time, whisking all the while.
Pour your curd mixture into the tart case and leave to set. This should take around 4-5 hours, so try to be patient – we know how hard it can be to resist!