Scale and clean fish; rinse well.
Remove fish meat and bones, taking care not to damage the skin, head and tail.
Put the raw fish through a meat grinder.
Cover fish bones in a kettle with water seasoned with salt, lemon juice and soup greens; cook 25 minutes.
Strain; reserve broth.
Heat butter in a skillet; add fish, parsley and crumbs and cook several minutes.
Mix in the onion, pepper, nutmeg, almonds and 2 egg yolks mixed with a little wafer.
Stuff mixture into fish skin; close fish with skewers, or sew with thread.
Lay fish gently into heated broth and simmer until done; remove to heated platter and keep warm while preparing the sauce.
Thicken broth in kettle with cornstarch mixed with a little cold water.
Stir the remaining 2 egg yolks into the sauce.
Add seasoning, if needed.
Pour sauce over fish on platter and garnish with lemon slices.