Heat your oven to 200°C/Fan 180°C/Gas 6. Peel and chop the potato. Peel and roughly chop the swede. Peel and chop the carrots.
Pop the veg in a pan. Pour in enough boiling water to cover them. Cover and bring to the boil. Turn the heat down. Simmer for 15-20 mins till the veg are soft when pierced with a fork.
Pop 4 of the sausages in a small roasting tin. Drizzle with ½ tbsp oil. Bake for 20-25 mins till browned and cooked through. Give the tin a quick shake halfway through cooking.
Peel and slice the onion. Warm ½ tbsp oil in a small pan. Add the onion. Season. Cook over a medium heat for 5 mins till soft and browned. Stir now and then.
Add 1 tbsp of the flour to the onions. Cook and stir for 1 min. Crumble in the stock cube. Pour in 300ml boiling water. Whisk till the gravy boils and thickens. Simmer for 2 mins. Take off the heat. Cover.
Cut the leaves off the tough kale stalks. Finely shred the leaves. Pop in a pan. Pour in enough boiling water to cover the kale. Simmer, without the lid on, for 5 mins till the kale is tender. Drain.
Drain the root veg. Tip back into the pan. Mash in the butter over a low heat till smooth. Season with salt and pepper. Serve the mash with the sausages, kale and onion gravy.