This cream sauce goes well with calf's tongue and boiled chicken.
- Mix the flour with a little cold water to make a paste.
- Bring the beef stock to the boil and bind it with the flour paste.
- Leave to boil for a short while and take off the heat.
- Add the cubed butter.
- Beat the egg yolk with the cream, and pour some of the warm sauce in with the mixture in small amounts, beating all the time.
- Add this mixture back in with the rest of the sauce and add pepper, salt and lemon juice to taste.