Preheat the oven to 220°C, fan 200°C, gas 7. Put the onions into a roasting tray with the vinegar and a little seasoning. Sit the sausages on top and roast for 20-25 minutes, stirring halfway through, until the onions and sausages are golden brown.

Meanwhile, put the potatoes in a pan of cold water with plenty of salt and bring to the boil. Once boiling, cook for 8-10 minutes until almost breaking apart. Drain and steam dry for a minute.

Pour the beef stock over the sausages in the tin and put it back in the oven for a further 10 minutes until reduced slightly (it won’t be thick like regular gravy).

Mash the potatoes with a masher or ricer, and add the butter, seasoning and grated cheese. Stir to melt the cheese into the mash, then add the Marmite. Give everything a really good stir again until the Marmite is rippled through.

Serve the sausages, mash and onion gravy in bowls with a scattering of parsley.