Preheat oven to 350°F.
Add butter to a skillet over medium high heat. Toss in celery, onion, and carrots and stir to coat in the butter. Cook for approximately 5 minutes or until veggies are tender and fragrant.
2 teaspoons salted butter, 1/4 cup celery, 1/4 cup onion, 1/4 cup carrots
Mix in the flour and curry powder and stir to coat. Once the veggies are coated and a paste forms, stir in the chicken broth. Bring to a boil, reduce heat to low, and allow to thicken for about 1-2 minutes, then remove from the heat.
1 tablespoon all purpose flour, 1 teaspoon curry powder, 1/2 cup chicken broth
Stir in the sour cream and the sliced chicken breast. Set aside.
1/2 cup light sour cream, 1 cup sliced curry chicken
Lightly flour a work surface and roll out the puff pastry sheets. Use the bottom of a glass or a 3" round cookie cutter to cut out circles in the dough. The two sheets should yield about 18 circles total.
2 sheets frozen puff pastry
Add 1 tablespoon of the chicken mixture to one-half of each circle. Moisten the edge of each circle with a small amount of water, and then fold over the dough to cover the mixture and press to close. Use a fork to seal each pie, and lay on a greased baking sheet, about 1" apart. Repeat with the remaining dough.
In a small bowl, combine whisked egg and water. Brush each hand pie with egg mixture and then sprinkle lightly with flaky sea salt.
1 egg, 2 tablespoons water, flaky sea salt
Bake for 18-20 minutes or until crisp and golden. Serve warm and enjoy!