Cut the lamb into bite sized pieces and dredge in flour seasoned with salt and pepper.
Cook bacon in a large frying pan until the fat is rendered, then add lamb and cook until browned on all sides.
Remove from pot.
Add onion and garlic, cook for 5 minutes, then add wine, bay leaf and sage and bring to a boil.
Return the lamb to the pot and lower the heat.
Simmer, covered, for 1 hour until lamb is tender.
Put egg yolks in a bowl and beat until light yellow, then stir in lemon juice.
Remove lamb to a heated platter and bring sauce to a boil for a few minutes.
Take off the heat and add a few spoonfuls to the egg mixture.
Whisk this mixture into the sauce and continue to whisk until the sauce has thickened.
Pour the sauce over the lamb, garnish with parsley and serve.