Put the court-bouillon in a saucepan, bring to the boil and add the desalted cod, let poach for 10 minutes, drain and set aside. Keep 40 cl of court-bouillon.
Melt the butter in a casserole. Add the baby onions, the juliennes of vegetables, the bacon bits and the mushrooms to sauté over medium heat until golden brown. Dust with flour, moisten with the reserved court-bouillon and stir well. Salt, lightly add the coarse cracked pepper, simmer for 10 minutes.
Whip the cream and the egg yolk in a bowl, pour this mixture into the pan, stir without letting it boil.
Adjust the seasoning.
Add the cod cut into large cubes to warm up. Pour into a deep serving dish, sprinkle with chopped parsley and serve immediately.
You can serve with toasted croutons.
