In a deep skillet, cook pork in butter over low heat for 8 to 10 minutes, until the pork is browned. Add the onions, mushrooms, garlic, salt and pepper. Cook and stir for 10 more minutes. Sprinkle the flour over the pork and stir. Add the wine, broth, leek, carrot, and celery and mix well. Add the parsley, thyme and bay leaf. Stir in the lemon juice.
In a small bowl, stir together the whipping cream and yolks. Slowly whisk in about ½ cup of the hot mixture into the egg yolk mixture. Slowly whisk in another ½ cup. Return to this mixture to the pan, stirring constantly. Heat and stir until slightly thickened and bubbly.