Wash the liver and dry it. Fry the onion in vegetable oil for 3-4 minutes, medium heat. Add the liver and cook over medium heat for 7-10 minutes.
Add the cream and simmer for 3 minutes.
Pour in the broth, salt and pepper to taste, pour in the cognac, add the nutmeg and put out for 3 minutes, minimum heat. Then cool slightly.
Punch the warm mass with a blender until smooth. Add the mustard and stir.
For festive serving, put the pate in a cooking bag with a nozzle. Put it on crackers or pieces of dried bread.