Wash leeks very well to remove dirt hiding between layers, then slice them thinly with care on your board.

Melt butter in a large pan over gentle heat, add onion and leeks, and cook slowly until soft, sweet and fragrant.

Sprinkle flour over the soft leeks, stir very well and cook gently so the flour loses its raw taste completely.

Slowly pour chicken stock into the pan, whisk as you pour and keep stirring until the sauce becomes smooth and thick.

Stir in cream, then add salt, pepper and thyme leaves, tasting carefully so the flavors feel balanced and warm.

Add cooked shredded chicken into the sauce, stir gently to coat every piece, and let it simmer so flavors come together beautifully.

Pour the creamy chicken and leek filling into your pie dish evenly, smoothing the top so pastry sits flat and neat.

Lay puff pastry sheet over the dish, trim edges, press gently and crimp sides so steam stays mostly inside while baking.

Brush pastry with beaten egg for shine, cut small slits on top carefully, so steam escapes and crust bakes crisp.

Place pie in hot oven at 200°C, bake until pastry turns golden, puffed and beautifully crisp with bubbling filling inside.