Make PIe Dough. Cut butter into small cubes. Freeze. Mix flour, salt, sugar in food processor.
Add butter evenly in flour mixture. Process just until you have large pea size pieces. Stream in water, slowly and stop as soon as dough forms. Flour your hands, take out dough and if it’s too wet, four each ball (make two and wrap in plastic overnight. You can make the same day, but refrigerate at least 30 minutes.
Preheat oven to 400 degrees.
Roll out, making sure you have a somewhat thick bottom (cast iron will make sure it cooks).
Make Pie Filling.
Mix sugar, cinnamon sticks, vanilla, nutmeg and blackberries together.
Taste your berries. Make them sweeter than you think you need to, as blackberries get more bitter when cooking.
Add in tapioca.
Cut dough into two circles, one large than the other. Roll out bottom and place in pan.
Roll out remaining and cut into strips. Place in lattice pattern.
Bake at 400 for 1 hour for medium size pie.
Cut off dough that hangs over pie. Roll out remaining dough and cut strips. Place over pan in lattice pattern. Brush with milk and sprinkle some sugar.
I like to use raw sugar, but you can use regular sugar. If you use a larger cast iron pan, double the ingredients in the recipe and bake for 1 hour, 15 minutes.