Preheat the oven to 425 degrees F. Line 2 baking sheets with parchment.
Melt the butter in a large skillet over medium heat. Add the chicken, celery, carrots, onion and some salt and pepper. Cook until the vegetables just begin to soften, about 7 minutes.
Meanwhile, make the crusts. Unroll both sheets of pastry, even out the surface with a rolling pin and cut out 3 circles from each. Transfer the circles to the prepared baking sheets, poke them all over with a fork and brush with the egg wash. Sprinkle over some salt and pepper. Bake until golden brown, about 10 minutes.
Meanwhile, sprinkle the flour over the chicken and vegetables and add the turmeric; cook for 2 minutes. Pour in the hot stock, add the half-and-half, peas, thyme and rosemary and cook until the sauce thickens, another 3 minutes. Serve in bowls topped with the crusts.