Preheat oven to 450 degrees. Lightly grease an 8 x 8-inch baking pan.
In the work bowl of a food processor, combine the flour and salt. Quickly cut the butter and shortening into the dry mixture until the size of small peas. Dribble in the ice water a little at a time and process quickly to moisten the mixture until it starts to come together. This pastry can be made ahead of time and refrigerated between two sheets of waxed paper until ready to use.
Roll out the pastry into a large sheet, approximately 20 x 12. Lay into the prepared baking dish, gently tucking it into the corners and allowing the extra to hang over the sides.
Spread the blueberries evenly in the baking dish. Dot with the diced butter. Sprinkle with 1 1/2 cups of the sugar. Flip the overhanging pastry over the blueberries to make a top. If pieces break off, just set them on top. The cobbler should look rustic. Sprinkle the remaining 1/2 cup sugar over the pastry.
Place in preheated oven and immediately reduce heat to 425 degrees. Bake for 45 minutes, until dough is golden brown and berry juice bubbles up.
Serve with warm vanilla ice cream.