Heat some oil in a large frying pan and cook the diced onions for about 5 minutes, stirring occasionally until they soften.
Add in the garlic, sage and apple then cook for a further minute.
Pour in the vegetable stock, then add in the butter beans. Leave it to simmer on a low heat whilst you cook the sausages.
In a separate frying pan, pan fry the sausages until they are browned all over.
Get the sausages into the bean stew, cover it with foil then simmer for about 15 minutes.
Take the foil off then stir in the baby spinach until its wilted.
Add in the mustard, crème fraiche, parmesan and the zest and juice of the lemon. Give it a stir and taste for seasoning.
Dish it up and enjoy.