2 apples (about 280g/10oz), peeled and chopped into small chunks
3 tbsp milk
Cook the potatoes in boiling, salted water for 15 mins until tender. Meanwhile, heat a non-stick frying pan and add the sausages. Cook over a medium heat for 15-20 mins, turning occasionally, until cooked through. Remove from the pan and keep warm.
Add a knob of the butter and the onion to the pan, then cook for 15-20 mins until soft. Stir in the flour, then gradually add the stock, stirring to make a sauce. Simmer for 2 mins, then pour into a jug and keep warm.
Cook the apples in half the remaining butter for 5-10 mins until softened. Drain the potatoes and mash well with the rest of the butter and the milk. Fold in the apple, then serve with the sausages and onion gravy.