Preheat oven to 375 degrees
Bring a large pot of water to a boil on the stove Add the peaches into the boiling water, a few at a time, and let sit for 45 seconds. Remove with a slotted spoon and set aside to cool. Repeat with remaining peaches. Once peaches have cooled enough to hold, peel of the skins and then cut them up into slices and discard the pit. Transfer sliced peaches to a large bowl. Add the blackberries, flour, lemon juice and zest, salt and brown sugar and toss together. Transfer fruit mixture into a large skillet and transfer into the oven, bake for 10 minutes and remove.
Combine the flour, brown sugar, baking powder, cinnamon and salt in a medium bowl. Cut in the chilled butter with a pastry cutter. Mix in the egg, buttermilk and vanilla and set aside.
Pile the topping onto the partially cooked fruit mixture using a spoon and randomly dropping scoops along the surface of the cobbler.
Place dish into the oven and bake for about 30 minutes until the top is slightly puffed and golden brown. Let cool for about 10 minutes before serving. Serve with vanilla ice cream.