Heat the oven to gas 6, 200°C, fan 180°C. Put the sausages in a roasting tin along with the onion wedges. Roast for 20 minutes.
Mix together the mustard and maple syrup. Take the roasting tin out of the oven, add the apple and sage and pour over the syrup mixture.
Return to the oven and roast for a further 20 minutes, until the sausages are plump and golden. Serve with mashed potatoes and buttered cabbage (shred, boil for 2 minutes, drain then toss in butter).
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