Bring the broth to the boil, add the chicken fillet and bay leaf, cover and leave to simmer over a low heat for 20 minutes.
Remove the chicken from the broth and dice into approx. 1 cm cubes. Melt butter in a saucepan. Sweat in the flour while stirring. Deglaze with white wine, then gradually pour in 400 ml of stock through a sieve while stirring. Pour in the cream, bring to the boil and simmer over a mild to medium heat for 15 minutes, stirring several times.
Preheat the oven to 180 degrees (160 degrees for a fan oven). Let peas thaw. Clean and quarter the mushrooms.
Place the pies on a baking sheet and bake in the hot oven on the middle shelf for 5-8 minutes. Season the sauce to taste with salt, pepper, Worcestershire sauce and lemon juice. Add the chicken, mushrooms and peas to the sauce and simmer for 4-5 minutes. Use a teaspoon to loosen the puff pastry tops from the pies and lift them out. Pick and chop the parsley leaves. Arrange the ragout fin in the pies and serve sprinkled with parsley.