To prepare filling, combine first 5 ingredients; set aside.
To prepare pastry, lightly spoon flour into dry measuring cups; level with a knife.
Combine 1/2 cup flour, ice water, and vinegar, stirring with a whisk until well blended to form a slurry.
Combine 1 1/2 cups flour, powdered sugar, and salt in a bowl; cut in shortening with a pastry blender or 2 knives until mixture resembles coarse meal.
Add slurry; toss with a fork until moist. Gently press mixture into a 4-inch circle.
Place dough on 2 sheets of slightly overlapping plastic wrap on a slightly damp surface. Cover dough with 2 additional sheets of plastic wrap.
Roll dough, still covered, into a 16 x 12-inch rectangle. Slide dough onto a baking sheet; place in freezer 10 minutes or until the plastic wrap can be easily removed. (Keep chilled until ready to use.)
Preheat oven to 40
Remove top sheets of plastic wrap.
Place dough, plastic wrap side up, on a flat surface.
Remove remaining sheets of plastic wrap.
Cut pastry into 12 (4-inch) squares.
Place about 1 tablespoon filling into center of each square. Moisten the edges of squares with 1 tablespoon milk; bring 2 opposite corners together. Press edges together with a fork to seal, forming a triangle.
Place triangles on a large baking sheet.
Brush tops with 1 tablespoon milk; sprinkle evenly with granulated sugar.
