First, preheat the oven to 400°F (200°C). Line it in a 9-inch pie dish with one crust.
Now, take a bowl. Mix berries, sugar, cornstarch, lemon juice, and salt in it.
Pour the filling into the crust and add butter pieces on top.
Then cover with the second crust, seal the edges, and brush it all with the eggwash.
Now cut them into small slits and let them bake for 40 to 45 minutes.
Cook them for 2 hours and serve them warm.