Prepare the Empanada Dough:

1. Mix Dry Ingredients: In a large bowl, combine the flour, salt, and sugar. Stir until evenly mixed.
2. Add the Butter: Add the cold, cubed butter to the flour mixture. Using your fingers or a pastry cutter, rub the butter into the flour until it forms a crumbly texture with pea-sized bits of butter.
3. Add Wet Ingredients: Slowly add the cold water (and vinegar if using) to the dough mixture, a tablespoon at a time, until the dough starts to come together. You may need to adjust the amount of water slightly to achieve a firm but not sticky dough.
4. Knead the Dough: Once the dough has formed, gently knead it on a floured surface for about 1-2 minutes until smooth. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes to chill.

Prepare the Chicken Filling:

5. Cook the Vegetables: In a large skillet, heat the olive oil over medium heat. Add the onions, garlic, and red bell pepper. Sauté for 5-7 minutes until softened.
6. Season the Filling: Add the shredded chicken to the skillet and season with cumin, paprika, cinnamon, salt, and pepper. Stir to combine. If using peas, add them now, and continue to cook for an additional 2-3 minutes.
7. Bind the Filling: Remove from heat, and stir in the beaten egg, cilantro, or parsley if using. This will help hold the filling together when you bake the empanadas. Taste and adjust the seasoning as needed. Add a squeeze of lime juice for a touch of zest, if desired.

Assemble the Empanadas:

8. Roll Out the Dough: Once the dough has chilled, roll it out on a lightly floured surface until it’s about 1/8-inch thick. Use a round cutter (or a bowl) to cut out circles about 4-5 inches in diameter.
9. Fill the Empanadas: Place a spoonful of the chicken filling in the center of each dough circle. Be careful not to overfill them.
10. Seal the Empanadas: Fold the dough over the filling to create a half-moon shape. Use your fingers to pinch the edges together, and then crimp them with a fork to ensure they are sealed tightly.

Bake or Fry the Empanadas:

11. Prepare for Baking: Preheat your oven to 375°F (190°C). If baking, place the empanadas on a parchment-lined baking sheet. Brush each empanada with a beaten egg to give them a golden, shiny finish.
12. Bake: Bake for 25-30 minutes, or until the empanadas are golden brown and crisp.
13. For Frying (optional): If you prefer fried empanadas, heat oil in a deep pan to about 350°F (175°C). Fry the empanadas in batches, turning them occasionally, until golden and crispy (about 4-5 minutes per side). Drain on paper towels.

Cool and Serve:

14. Cool: Let the empanadas cool for a few minutes before serving.
15. Serve: Serve warm with your favorite dipping sauces, like salsa, garlic sauce, or even a tangy yogurt-based sauce.