For the Bangers:

1. To a cast iron skillet add the 1 tablespoon vegetable oil over medium heat.
2. Sauté the sausages, turning frequently until evenly browned.

For the Mash:

1. While the sausages are cooking, fill a large pan with water and add the potatoes and bring to a boil. Once boiling add a large pinch of salt and simmer for 15 minutes until they feel tender when pierced with a fork.
2. Once the sausages are done, remove and set aside.

For the Onion Gravy:

1. Add 2 tablespoons butter and 1 teaspoon oil to the pan used to cook the sausage over medium heat.
2. Once the butter is melted add the onions and salt and sauté, turning often until the start to soften and slightly brown.
3. Mix the flour into the butter and onions until well mixed.
4. Stir in the stock, English mustard, and Worcestershire sauce until well mixed and bring to a low simmer until thickened.

To Serve:

1. Add the sausages to the gravy and allow to heat through.
2. Put the cooked potatoes into a large bowl and mash.
3. Stir in the remaining 1 tablespoon of butter, melted, warm milk, salt and pepper.
4. Place mashed potato onto a plate and top with the bangers and onion gravy.