Heat the oil in the casserole then, with the heat at medium, brown the sausages evenly all over.
Transfer them to a plate while you saute the garlic and shallots.
Return the sausages to the casserole, pour in the wine and the thyme and bay leaves. Now season lightly, bring it all up to a gentle simmer, cover, turn the heat as low as possible and let it all simmer gently for 30 minutes.
For the Onion Marmalade:
Peel and slice onions thinly.
Melt the butter until a nut brown
Add onions and sugar, season and stir well
Cover and cook slowly for approx 30 minutes
Add vinegar and wine, stir and cook uncovered for a further 30 minutes.