Prick sides and bottom of pastry with a fork. Bake in a preheated hot oven until golden, 10-12 minutes, cool. In a medium saucepan combine 2 cups of the blueberries, both sugars, flour, butter, salt, and lemon juice. Cook and stir over low heat until mixture boils then thickens. Stir in remaining 3 cups of blueberries and vanilla extract.
Dust berries with part of flour.
Cream shortening, and add sugar gradually. Then add eggs mixing well. Add flour and milk alternately to dough mixing will after each addition. Fold berries into batter last, put in greased 9 X 13 pan. Sprinkle with 2 T sugar.