Soak the peas in water overnight.
The next day, mix with the soaking water with boiling water in a pot and bring to a boil.
After 10 minutes, reduce heat and add hot water. Continue to simmer slowly. When peas are soft, mash.
Prepare a roux with butter and flour, deglaze with cold water or diluted beef broth. Season with salt and nutmeg (freshly grated). Bring to a boil and refine with egg yolk and whipped cream.
Add the pea puree and mix well. Dilute with beef broth if necessary.