Method:

1. Heat ghee in the pan and brown the sausages on all sides. (How many sides does a sausage have? ¯\_(ツ)_/¯) Remove sausages from the pan and set aside.
2. Add more fat to the pan if there isn't much remaining from the sausages. Add the sliced onions, and cook slowly, stirring occasionally, until all their natural sweetness has released and they are nicely caramelised.
3. In the meantime, cut up potatoes and place in a pot of generously salted boiling water to cook through.
4. Back to the pan of onions: stir through some black pepper, a tablespoon or so of mustard, and the broth. Bring to a boil, and let the liquid reduce for 10 minutes without the lid on.
5. Make a slurry by stirring together the arrowroot powder with a splash of cold water. Stir this smooth white paste into the gravy. Increase the heat, stirring, until the gravy has thickened to your liking. Make up more of the slurry if it's not thickened enough. Take care not to boil aggressively though, as arrowroot is heat sensitive and loses its thickening properties when overheated.
6. Add back the sausages to the gravy and allow to cook through gently with the lid on.
7. Mash the potatoes, stir in tons of butter and season generously.
8. Serve up the mash, top with sausages and lashings of gravy.