Preheat the oven to 350°F / 175°C (180°C fan-forced).
Using a rolling pin, roll each pastry sheet slightly if needed. Cut into circles approximately ½ inch (1cm) larger than the diameter of your oven-proof dishes.
Place the pastry circles on a parchment-lined baking sheet, brush with egg wash, and bake at 400°F / 200°C (200°C fan-forced) for 15-18 minutes or until deeply golden brown, puffed, and crisp. Set aside.
Season the chicken with seasoned salt and black pepper.
Sauté the chicken in the oil in a large skillet over medium-high heat for 5-7 minutes per side, or until the internal temperature reaches 165°F / 74°C and the juices run clear.
Chop the cooked chicken into ½ or 1-inch chunks.
Melt the butter in a pot, then sauté the minced onion for 3-4 minutes until softened and translucent. Add the minced garlic and cook for 30 seconds until fragrant.
Add the flour slowly, stirring constantly to form a roux. Cook for 2-3 minutes until it thickens and turns a light blonde color.
Add the cream slowly, stirring constantly.
Add the dissolved chicken base and stir, then simmer for 2-3 minutes until the sauce is thick enough to coat the back of a spoon.
Stir in the chicken, peas, carrot, and a pinch of nutmeg if liked.
Spoon the chicken mixture into 4 oven-proof dishes and top each with one of the baked pastry lids.
Bake at 350°F / 175°C (180°C fan-forced) for 5-10 minutes until the filling is bubbling around the edges. Serve right away.