How to Make It
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, baking powder, and 1/4 teaspoon salt in a food processor; pulse 2 times or until combined. Add butter; pulse 4 times or until mixture resembles coarse meal. With processor on, slowly add 1/2 cup ice water and vinegar through food chute, processing just until combined (do not form a ball). Gently press mixture into 2 (5-inch) circles on plastic wrap; cover. Chill for 1 hour.
Remove chorizo from casings. Cook chorizo in a large nonstick skillet over medium-high heat until browned, stirring to crumble.
Place potato in a saucepan; cover with water. Bring to a boil. Reduce heat, and simmer for 8 minutes or until tender; drain. Place in a large bowl; mash with a potato masher. Add chorizo, paprika, and remaining 1/4 teaspoon salt; stir until well combined.
Preheat oven to 425°.
Remove dough from refrigerator, and halve each disc. Place 1 dough portion between 2 sheets of wax paper. Roll into a 1/4-inch thickness; cut 2 (3-inch) circles with a biscuit cutter. Repeat procedure with the remaining dough portions. Combine excess dough, roll to 1/4-inch-thickness, and cut 4 (3-inch) circles with a biscuit cutter. Working with 1 circle at a time (cover remaining circles with a damp towel to prevent drying), spoon 1 tablespoon potato mixture into center of each circle; fold dough over filling. Press edges together with a fork to seal. Place empanadita on a large baking sheet coated with cooking spray. Repeat with remaining dough circles and potato mixture. Combine remaining 1 tablespoon water and egg white. Lightly brush tops of empanaditas with egg mixture. Bake at 425° for 20 minutes or until lightly browned.