In a glass or heatproof bowl, whisk together the eggs, sugar and salt.

Place the bowl over a pan of simmering water. Add the butter and continuously stir until all the butter is melted.

Keep whisking the mixture over the heat for around 10 minutes. Add the lemon juice and blueberries. Whisk for about 5 minutes more until it thickens and the blueberries start to burst. (Do not worry if they are still intact)

Prepare a large bowl with a sieve on top. Gently sieve the curd and squeeze all the blueberries. This skin of the blueberries should remain in the sieve whilst the juices fall down in the curd. Mix the curd until the juices from the blueberries are well combined.

Pour the curd into a glass jar and set aside in the fridge until ready to use.

In a large bowl mix the flour and the cubed butter to a crumbly mixture. Work with your fingertips so that you don’t melt the butter.

Add the icing sugar and the lemon peel and combine well.

Form a well with the ingredients, put the egg in the middle and start mixing. Knead the dough briefly until all the ingredients are incorporated and a smooth dough is formed.

Wrap in cling film and let it rest in the fridge for at least 30 minutes.

Meanwhile preheat the oven to 180°C or 350°F. Line a baking tray with parchment paper. Set aside.

Roll out the dough on a floured surface until it's about 0.5 cm thick. Cut the dough with a smaller cutter and cut out the centre of half of the biscuits.

Transfer to the baking tray, leaving some space between one another, and bake for about 20 minutes, until they turn slightly golden brown at the edges.

Leave to cool at room temperature on a cooling rack.

Once all the biscuits have cooled a little but are still a bit warm, dust the biscuits having the cut out centre, with icing sugar.

Add about a teaspoon of lemon curd to each of the full biscuit and place the cut out centre biscuit on top of the curd. Thus, sandwiching the curd between the two biscuits.