Remove the sausages from their skins and form each sausage into four balls.
Slice the onions (2 onions), roughly chop the mushrooms (200g) and finely chop the garlic (2 cloves).
Heat the olive oil (1 tbsp) in a large saucepan, add the sausages and cook until they are browned on the outside.
Once the sausages have browned, remove them from the pan and set aside.
Add the onions and mushrooms to the pan, reduce to a low heat and cook for 3 minutes.
Add the garlic and cook for a further minute.
Add the cider (400ml) and bring to the boil. Return the sausages to the pan, cover and cook for 10 minutes.
Add the creme fraiche (175ml) and mustard (2 tbsp) and cook for 5 minutes.
Season with salt and pepper.
If you're cooking this dish to chill/freeze and reheat later, remove from the heat now. Otherwise, continue to cook for roughly 10 minutes until the sauce has reduced.