Preheat oven to 400°.
To prepare filling, cook plantain in boiling water 10 minutes or until tender; drain. Combine plantain and condensed milk in a bowl, and mash with a potato masher. Set aside.
To prepare the dough, 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, tossing with a fork until moist.
Gently press dough into a 4-inch circle on 2 lengths of heavy-duty plastic wrap; cover with additional overlapping plastic wrap. Roll dough, still covered, into an 18 x 12-inch rectangle; freeze 10 minutes or until wrap can be easily removed. Remove wrap; place dough on a lightly floured surface. Cut dough into 24 circles using a 3-inch round cutter.
Place circles on a baking sheet coated with cooking spray, and lightly moisten edges of dough with water. Spoon 2 teaspoons plantain mixture into each circle. Fold dough over filling; pinch edges together to seal. Brush the tops of dough evenly with 1 tablespoon 2% milk; sprinkle evenly with granulated sugar.
Bake at 400° for 17 minutes or until lightly browned. Combine the chips and 2 teaspoons 2% milk in a small bowl, and microwave on high for 30 seconds; stir until smooth. Drizzle melted chocolate over empanaditas. Serve warm.