Preheat oven to 425 degrees. Place the blackberries in a 7×11 baking dish or pie pan. In a separate bowl, combine the sugar, pinch of salt, and flour. Add the egg and stir with a fork, then use your fingertips to form a crumbly, sandy mixture. Scatter this over the berries. Using a sharp paring knife, slice the butter as thinly as you can and shingle it over the flour mixture in a single layer. Bake for 25 minutes or until the berries are bubbly and the cobbler topping is nicely browned. Serve warm, with ice cream.