Method

1. Cut a slit into each chicken breast to form a pocket.
2. Melt the butter and fry the shallot until soft.
3. Add the mushrooms and cook gently for 2-3 minutes
4. Allow to cool slightly.
5. Add the hazelnuts, egg white and cream to the shallots and mushrooms and season.
6. Place each chicken on a buttered circle of greaseproof paper large enough to enclose it.
7. Fill each chicken breast with  some of the stuffing mixture and sprinkle a tsp of sherry over each peice of chicken and seal the parcels.
8. Place on a baking tray and bake at 180C /  Gas Mark 4 for 40 minutes.
9. Meanwhile make the sauce.  Melt the butter and stir in the flour.  Cook for 1 minute.
10. Remove the pan from the heat and gradually stir in the stock.
11. Bring to the boil and simmer for 5 minutes, stirring occasionally.
12. Mix the egg yolks with the cream.
13. Remove the pan from the heat and stir a little of the stock int o the egg mixture.
14. Stir the egg mixture into the sauce and heat.
15. Adjust the seasoning and stir in the sherry.
16. Serve with the chicken breats.