For the sausages, place all the ingredients, except the olive oil, into a bowl and mix thoroughly then season well with salt and freshly ground black pepper. (Fry a tiny bit of the mixture in a hot pan with a little olive or sunflower oil to check the seasoning. Add more if required.)
Divide the mixture into 12 pieces and shape each one into a sausage shape. Place on a baking tray or plate and set aside until you want to cook them. (Chilling them for a day in the fridge is fine, or you can freeze them.)
To cook the sausages, heat a frying pan on a low to medium heat, add two tablespoons of olive or sunflower oil and gently fry the sausages for 12-15 minutes, turning occasionally, until golden on all sides and completely cooked through.
For the colcannon, cook the potatoes in boiling salted water for 10 minutes, then drain off three quarters of the water and continue to cook over a low heat until tender.
When cooked, drain all of the remaining water. Once just cool enough to handle, peel the potatoes, then mash with half of the butter.
Heat a pan until hot and add the remaining butter, two tablespoons of water and the sliced cabbage. Cook over a medium heat for 5-7 minutes, stirring frequently, until just cooked through.
Add the cabbage mixture to the potatoes, then add most of the hot milk and the parsley, keeping some of the milk back in case you do not need it all. Season, to taste, with salt and freshly ground black pepper, and beat until creamy and smooth, adding more milk, if necessary, to achieve your preferred consistency.
For the apple sauce, place the apple in a small pan with the water. Cover with a lid and cook over a gentle heat, stirring occasionally, until the apple has broken down to a pulp. Add sugar to taste.
To serve, place a spoonful of colcannon onto each plate and place a knob of butter into the centre to melt. Add three sausages to each plate and a spoonful of warm apple sauce alongside.