Saute the onion in the butter in a saucepan until tender and golden.
Add the apples, celery, parsley and leeks.
Cook two minutes.
Sprinkle with the curry powder and cook two minutes longer.
Sprinkle the flour over the vegetables.
Add the bay leaf, thyme and salt.
Gradually stir in the stock.
Bring the mixture to a boil, cover and simmer gently two to three hours.
Put the sauce through a food mill or puree in an electric blender.
Return the pureed sauce to the pan and stir in the seafood and one-half cup of the heavy cream.
Reheat the mixture and stuff the crepes with it.
Spoon the remaining sauce over one-half of each crepe.
Combine the escoffier sauce with the remaining cream and the worcestershire sauce.
Heat and spoon over the other half of each crepe.