Cook potatoes in boiling water until soft (about 20 minutes). Drain and mash with butter, mustard, cream, salt & pepper to taste.
Heat oil in a hot grill skillet, cook sausage until cooked through. Set aside in a warm oven.
For the onion gravy: Heat 1 tablespoon butter over medium heat in skillet, add onions and flour and cook until soft. Add 3 cups beef broth and 1 cup red wine. Simmer until reduced for 10 minutes. Season with salt & pepper.
To serve: Scoop one cup mashed potatoes onto serving dish, top with two bangers and pour over onion gravy. and drink a Guiness while your at it:)
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