If making homemade pie crust; make the pie crust and get it really well chilled.
In a large bowl use a large spoon to combine the blackberries, sugar, tapioca, cinnamon, nutmeg, lemon juice and zest.
Butter or spray with cooking spray a 9x13-inch baking dish.
Add the blackberry mixture. Scrape all the sugar and tapioca out of the bowl with a rubber spatula.
Cut the butter into pieces and distribute evenly over the blackberry mixture.
Cut pie dough into wide strips. (about 2-inches wide)
Lay pie crust strips across one length of the baking dish.
Pull back every other pie strip. Add a pie crust strip going the opposite direction.
Repeat this process until the entire baking dish is covered.
Use a pastry brush top of pie crust with an egg wash. Sprinkle with granulated or turbinado sugar.
Bake in a preheated 400 degrees F oven for about 60-65 minutes. Or until the filling is bubbling up nicely and the pie crust is golden browned.
Remove the baking pan from the oven and let cool for 30 minutes prior to serving, which will help the filling set properly.
Serve with a scoop of vanilla ice cream if desired.
Notes
Blackberry cobbler
You can use homemade or store-bought pie crust.Set the baking dish on a half sheet pan lined with parchment paper to catch any berry juices that might overflow.Turn the baking dish fully around half way through the baking process to evenly brown the crust and cook the filling.Use fresh or frozen blackberries for this cobbler.I used about 4-5 pints of fresh blackberries from the farmers market. Which is about 6 cups of blackberries.If using frozen blackberries you do NOT need to thaw them!Cobbler will keep for a few days stored in the refrigerator.