Pre-Preparation: In a bowl, mix the chicken pieces with dried rosemary, cayenne powder, salt, and all-purpose flour. This step infuses the chicken with flavor and helps in thickening the sauce later. Boil and peel the potatoes. Mash them with butter, milk, salt, and pepper until smooth and creamy. Set aside.

Cooking the Filling: In a pan, heat butter and oil. Add the marinated chicken pieces and cook until golden brown. Remove and set aside. In the same pan, add a bit more butter if needed. Sauté minced garlic, chopped onions, carrots, and bell peppers until softened. Sprinkle all-purpose flour over the vegetables and cook for a minute. Gradually add milk, stirring continuously to avoid lumps. Season with salt and pepper. Add the cooked chicken and frozen peas to the sauce. Let it simmer for 10-15 minutes until the sauce thickens. Stir in chopped parsley or coriander.

Assembling and Baking: Transfer the chicken and vegetable mixture into a baking dish, spreading it evenly. Spoon the mashed potatoes over the filling, spreading it to cover completely. Use a fork to create a textured surface. Preheat the oven to 200°C (392°F). Bake the pie for 45 minutes to 1 hour until the top is golden and the filling is bubbling. Allow the pie to cool for about 15 minutes before serving. This helps the layers set and makes serving easier.