I used frozen strawberries, which make the filling quite juicy when leaving the fruit filling to come to room temperature. I dumped it all into the pie filling regardless and had a bit of spillage, but nothing that didn't clean up too badly. You can always use fresh fruit if you prefer.
Ingredients
For the pie crust
360g plain flour
2 tbsp caster sugar
1 tsp salt
230g cold unsalted butter, cubed
120ml buttermilk
For the filling
300g rhubarb, washed, top and tailed, and cut into 1cm slices
To make the pie crust, put the flour, sugar and salt in a bowl and mix together before adding the butter. Using your fingertips, break down the butter into chunks, as though you were making shortcrust pastry. Don’t rub in the butter too fine, you want the mix to be textured - some bits of butter rubbed in finely with other larger pea sized pieces.
Once roughly combined, stir through the buttermilk with a knife and bring together with your hands, adding a little flour if it feels too sticky. Divide into two and wrap in clingfilm and place in the fridge to rest for at least one hour. You can make this the day before, storing in the fridge before bringing to room temperature for around 20 minutes.
Once you are ready to make the pie, dust a clean work surface with flour and roll out one half of the pastry into a large circle slightly bigger than your pie tin. I used a 23cm tart tin and this worked fine. Once rolled, carefully lift the pastry into the tin and press down lightly into the corners. Fold the edges outward but inside the tin to create a rounded top, then place the pie in the fridge while you make the filling.
To make the filling, place the rhubarb, strawberries, sugars, cornflour, lemon zest and juice into a bowl then stir to combine. Leave to one side to allow the fruit to macerate. It may become a little juicy but don’t worry - even if a little spills out of the pie while baking it will still look and taste delicious.
Preheat the oven to 200oc/180oc fan as you assemble the pie. Pour the filling into the pie crust and level off with a spoon then place to one side as you make the lattice. Roll out the second pastry disc as before, cutting into 10 equal strips longer than your pie.
To make the lattice, I followed the tutorial linked above then made two plaits with the leftover pastry scraps.
Brush the lattice and the edges of the pie with the egg wash then place on a baking sheet lined with baking parchment and bake in the oven for 20 minutes then lower the temperature to 180oc/160oc and bake for a further 40 minutes until the pie crust is golden and crisp.
Remove from the oven and leave to cool in the tin for at least a couple of hours to let the juices settle.
Recipe by Victoria Sponge Pease Pudding at http://victoriaspongepeasepudding.com/baking/strawberry-rhubarb-lattice-pie/