Heat the oven
Preheat the oven to 180°C.
A cobbler with a bottom crust as well as a top one — shortening pastry, blackberries thickened with cornstarch, and a woven lattice over it.
The pastry can wait in the fridge
Roll the sheets out, lay them on floured parchment and keep them covered in the fridge until it is time to cut strips and weave. Cold pastry handles far better than warm.
Preheat the oven to 180°C.
In a large bowl, stir together the flour, granulated sugar and salt, mixing well. Add the chilled shortening and, using a pastry blender or a fork, work it into the flour until the mixture is crumbly and the bits of shortening are the size of peas.
In a medium bowl, whisk together the eggs, water and vinegar. Add most of the liquid to the flour mixture and stir with a fork until everything is evenly moistened and the dough holds together, adding more water if it needs it. Knead it in the bowl to bring it into a smooth ball.
The dough should hold its shape and be neither tacky nor crumbly and dry. If the mixture is too wet, work in a little more flour.
Lightly flour a large work surface and turn the dough onto it. Divide it in half and set half aside, covered with plastic wrap. Roll the other half out into a large rectangle, an eighth to a quarter of an inch thick. Roll it up on the rolling pin, then unfurl it over the baking dish, easing it onto the bottom and up the sides. Trim any excess, leaving a one-inch overhang.
If the dough tears, do not worry about it — just press it back together.
Flour the surface again. Take the remaining dough ball, cut it in half, and roll one half into a long rectangle of the same thickness. Cover it with a kitchen towel and set it aside. Flour the surface again, take the final ball, and roll it into a shorter rectangle. Cover that with another towel and set it aside.
For easier handling, transfer the sheets to floured parchment and keep them covered in the refrigerator until it is time to cut and weave.
In a medium bowl, combine the blackberries, brown sugar, lemon juice, cornstarch, cinnamon, vanilla and salt. Stir to mix well.
Pour the filling into the lined dish. Using a chef's knife, cut each reserved sheet of dough long-ways into even inch-wide strips. Lay the longest strips evenly across the length of the filling, then weave the shorter strips across the width to form a lattice top. Crimp the ends of the strips together with the bottom crust overhang, trimming off any excess.
Place the dish on a large baking sheet and transfer it to the oven. Bake until the filling has thick bubbling in the centre and the pastry is light golden brown. Let the cobbler rest for about ten minutes before serving.