Brown beef, stir in diced potatoes, cook covered, 8 mins, on low medium heat.
Mix flour and water in a small bowl
Take off lid, season beef, then pour in flour mixture, stir quickly (it will thickened). Add in chives, and take off pan from heat. Cool to room temperature.
Lay out thawed pastry, cut with round cookie cutter. Reroll scraps, and cut as well.
Place a tbsp of filling on one round skin, top with another, and seal edges. Poke skin with fork, then brush with yolk mixture. Repeat steps.
Preheat oven to 400 F and bake pockets for 15-20 mins