Preheat oven to 450 degrees F. Prepare Pastry. On a lightly floured surface, roll pastry into a 12-inch circle. Transfer to a parchment-lined baking sheet.
Meanwhile, in medium saucepan combine sugar, cornstarch, and salt. Stir in water and 1-1/2 cups of the blueberries. Cook and stir over medium heat until thickened. Remove from heat. Stir in remaining 2-1/2 cups blueberries and butter until butter is melted. Add in almond extract, lemon zest, lemon juice, and chopped fresh thyme. Cool completely.
Place fruit mixture in the center of the rolled out pastry and fold edges over the filling. Brush pastry with milk or an egg wash. Bake at 375 degrees F until pastry is golden brown and the filling is running. Cool on wire rack. If desired, cover and chill in refrigerator until ready to serve.
In bowl combine flour, sugar, and salt. Using a pastry blender, cut in shortening and butter until crumbly. Using fork, stir in ice water, 1 tablespoon at a time, until dough just starts to form. Knead 2 or 3 times in bowl. Wrap with plastic wrap and chill at least 30 minutes.