Heat a large frying pan with some oil and add in the sausages. Cook for 3 - 4 minutes on each side until the sausages are browned all over. If you wish (whilst you are waiting on the sauce) you can place the sausages into the oven at 150˚C at this stage for up to 10 minutes.
Meanwhile, in a same pan, drizzle extra oil, over medium heat. Add in the sliced onions and the herbs. Allow them to cook for 5-8 minutes until caramelised. Sprinkle some flour if desired and cook for a further minute or so.
Gradually add the cider or wine and stock and mustard at this stage and allow it to come to the boil. Simmer gently for 3 - 5 minutes.
Serve the sausages on top of the mashed potatoes and generously pour some of the onion gravy on the top. Enjoy immediately.
Keyword ireland, irish, Kevin Dundon, mash, potato, sausage, traditional