Peel and dice the onion, then fry until softened. Chop the garlic and apple and add along with sage
Cook for a minute, then pour in the vegetable stock and add the drained butterbeans
Pan fry the sausages until browned all over, then add to the stew. Cover with foil and simmer for 15 minutes
Stir in the spinach, mustard and crème fraiche. Simmer for a little longer, then grate and stir in the parmesan. Taste and add salt and pepper to taste, then add the lemon zest and juice. Serve and enjoy!