An easy, rustic citrus pie with condensed milk and a biscuit crust, this makes a great summer pudding which you can prepare in advance and leave to chill in the fridge. The inclusion of the beaten egg whites gives the lemon filling a lighter, more cloud-like texture.
I like to use these cinnamon barley biscuits for the base, but if pushed for time you could also use digestive biscuits or biscoff.
Line a 23cm loose bottom tart tin or spring form cake tin with greaseproof paper. Preheat your oven to 180°C.
Blitz the biscuits in a blender into a fine dust with no chunks (or you can use a rolling pin). Stir in the melted butter, cinnamon and sugar and combine. Spread this evenly into the base of the tin, and up the sides to form the crust. Really press it down with your hands to create a firm base. Bake for 10-12 minutes until golden brown, then set aside to cool.
Beat the egg whites in a large bowl until they form stiff peaks.
In a separate bowl, using an electric hand whisk beat the condensed milk together with the egg yolks for 6 minutes, until thick and creamy. Add the lemon zest.
Gradually pour in the lemon juice, beating all the time. Gently fold in the egg whites.
Pour the mixture into the tart case, and bake for 25-30 minutes, or until set in the centre. Leave it to cool fully, and then refrigerate it for at least two hours before serving.
This will keep for 2-3 days if stored in the fridge wrapped in cling film.