Bangers and mash, onion gravy

Pasos

1. Peel the potatoes, cut them into even pieces, then place them in a large pot of cold salted water; cook until a blade pierces them without resistance.
2. Meanwhile, thinly slice the onions; heat the oil with a knob of butter in a large skillet, then brown the sausages over medium heat until they are deeply golden on all sides.
3. Remove the sausages and keep them warm; put the onions in the same skillet with a pinch of salt, then melt them gently until they are amber, soft, and sweet to the nose.
4. Sprinkle the flour over the onions, mix until it loses its raw appearance, then gradually pour in the beef stock, scraping up the browned bits stuck to the bottom of the skillet.
5. Add the Worcestershire sauce, pepper, then return the sausages to the gravy; simmer over low heat until the sauce coats the back of a spoon and the sausages are heated through.
6. Drain the potatoes as soon as they are tender, return them briefly to the hot pot to evaporate the moisture, then mash them until you get a fine texture.
7. Fold in the rest of the butter, then the hot milk little by little, until you have a soft and creamy mash; taste and adjust with salt and pepper.
8. Serve the mashed potatoes in shallow bowls, place the sausages on top or alongside, spoon over generously with the onion gravy, and offer the English mustard on the side.