Step 1: Add the chicken, half of the thyme, potatoes, celery, and carrots to a large pan. Pour in the stock and heat through. After 15 minutes, lower the heat, cover, and cook gently.

Step 2: Clean the pan, put it back on the burner, and melt the butter. Simmer the onions for 5 minutes or until they are tender. To create a smooth, thick sauce, stir in the flour and then gradually add the conserved stock. Simmer for two minutes after adding the milk.

Step 3: Stir in the parsley, lemon juice, and leftover thyme after turning off the heat. Combine the ham, veggies, and chicken in a deep, ovenproof dish (ideally one with a lip or rim that holds 2.2 liters or 4 pints).

Step 4: After adding the sauce, let it cool a little. Set oven temperature to 200°C, gas 6, fan 180°C.   Roll out the crust until it is roughly 5 cm/2 in bigger than the dish’s top. Trim the pastry in a strip of 2.5 cm/1 in.

Step 5: Apply egg to the dish’s rim and press the strip firmly all the way around. Drizzle with egg, then carefully lift the pastry over it, pinching the edges to create a tight seal.

Step 6: After trimming off extra, use a fork to make all of the pastry’s edges visible. Create four little incisions in the middle.

Step 7: After brushing with egg, bake for 25 to 30 minutes, or until golden and crisp.