Heat a drizzle of oil in a large, non-stick pan. Add the chicken and fry on a medium heat, turning reguarly until no longer pink. Remove from the pan and set aside.

Add the butter and heat until melted.

Add the leeks and fry for 5 minutes until soft.

Stir in the flour and stir on a heat until it has disappeared

Slowly add the stock a little at a time, bringing it to the boil each time before adding more and stirring continuously.

Return the chicken to the pan with the mustard and oregano. Season with salt and pepper and give it a good stir.

Heat the oven to 190C fan.

Break each stuffing ball into 4 pieces, add them to the pan and gently fold them into the mixture so they don't get too broken up.

Cut out a circle of pastry 26cm wide (you may need to roll out the pastry a little)

Place the circle onto a lined baking tray.

Tip the filling over the pastry and spread it evenly, leaving a 2cm gap from the edge.

Cut out another pastry circle 30cm wide (you may have to cut off the short end and attach it to the top end to make it big enough)

Lay the pastry over the filling and press the edges together.

Use the prongs of a fork to mark indents all the way around the join. Trim the edge to neaten.

Brush with beaten egg.

Use the blunt side of a dinner fork to make faint lines from the middle to the outer edge.

Bake in the oven for 30 mins or until cooked through