Prick the sausages. De-rind and chop the bacon. Peel and thickly slice the onion or peel the shallots and leave whole. Wash the mushrooms and slice if large.
Heat the oil in a casserole or thick saucepan, over a moderate heat, and lightly brown the sausages. Remove them from the pan.
Add the bacon and onion, and fry for 2-3 minutes. Stir in the flour, and gradually add the wine, beer, cider or stock, stirring as the sauce thickens.
Return the sausages to the pan. Add the mushrooms, herbs, garlic, salt and pepper. Reheat, then put on the lid, lower the heat and leave to simmer gently for 35-45 minutes, removing the lid for the last 15 minutes of cooking time. Add a little more liquid if it gets too dry.