Cook the chicken breasts in a pot with water and salt. Once it comes to a boil, let it simmer for about 20 minutes (depending on the size of the breasts). Check if the chicken is cooked through and remove it from the pot. Once warm, shred the chicken using a fork and knife.
Place a large skillet over medium heat, add the olive oil, and sauté the onion and garlic until translucent. Add the bell pepper and leeks and cook for a few minutes until tender. Incorporate the shredded chicken, sweet paprika, salt, and pepper. Cook the mixture for about 5 minutes, stirring occasionally.Turn off the stove and add chopped, hard-boiled eggs. Stir to combine.
To make the empanada dough, combine the boiling water with the butter and salt in a bowl and mix until the butter melts. Add the flour and combine. Transfer the dough to a clean surface and knead for 15 minutes until it is very soft.
Roll out the dough and cut circles of 4 ½ inches. Preheat the oven to 425°F. Fill each empanada with a portion of the chicken filling, folding and crimping the edges to seal them. This folding is also known as "repulgue" in Spanish. The easiest way to do this is with a fork. Use the tips of the fork to press on the edges of empanadas gently. Place the empanadas on a greased baking sheet.
Finally, beat an egg and brush the tops of the empanadas with the egg wash. Bake for 15-20 minutes or until golden brown. Baking time will vary from one oven to the other. It's important to start checking the empanadas at the 10-minute mark.
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Notes
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