By hand, or using a paddle attachment on an electric mixer, combine all ingredients to form a soft dough. Do not overmix.
Wrap the dough well and refrigerate 10-12 hours before using.
When ready to use, remove dough from refrigerator and allow it to sit at room temperature 10-15 minutes before using.
Preheat oven to 350
Lightly butter a 9×13 inch baking dish
Allow the prepared pastry to come to room temperature one hour before preparing the cobbler.
Divide dough into half. On a floured surface, roll out one half of the dough into a 9”x13” rectangle, 1/2-inch thick.
Place the dough in a 9”x13” Pyrex baking dish and bake10 minutes. Remove the par-cooked dough from the oven and allow it to cool.
Place the berries in a large mixing bowl and sprinkle them with sugar and citrus juices. Gently mix. Combine flour and cinnamon together. Sprinkle the berries with the flour mixture and gently fold in. Spread the berry mixture over the top of the par baked pastry.
On a floured surface roll out the remaining dough into a 9”x13”rectangle. Using a sharp knife cut 1/2-inch wide strips. Arrange the strips into a lattice design atop the berries.
Whisk together the egg and milk and using a pastry brush, egg wash the dough. Place the prepared cobbler on a sheet pan and bake for 35-40 minutes. Allow to cool for 20 minutes before serving.