Argentinian Chicken Empanadas

Name: Argentinian Chicken Empanadas
Prep time: 40 min
Cook time: 3 h 40 min
Total time: 3 h 40 min
Yield: 14 pieces
Ingredients: 100 g water; 175 g unsalted butter; ½ tsp fine sea salt; 350 g plain flour; 1 tsp baking powder; 1 medium egg; 60 g onions; 1 garlic clove; 240 g chicken breast fillets, skinless; 1 red pepper; 8 pitted green olives; 30 g olive oil; 1 Tbsp tomato purée; 1 tsp smoked paprika; 1 tsp ground cumin; 1 tsp fine sea salt; ¼ - ½ tsp ground black pepper; plain flour; milk