Preheat the oven to 180℃ fan/200℃/Gas Mark 6.
Put the butter and onion in a small frying pan over a medium heat and cook for 5-10 minutes until slightly softened but not coloured.
Remove the skins of the sausages - cutting along the long edge of each sausage and then turning them inside out - and discard the skins. Put the sausage meat in a large bowl with the cooked onion (and the butter it cooked in) and all the remaining ingredients. Stir until thoroughly mixed (you may need to use clean hands!).
Spoon the mixture into a shallow ovenproof dish (don't smooth the top, as the lumps and bumps given a good texture).
Bake in the oven for 45 minutes, until cooked through and golden on top.
Did you make this recipe? Click here to let us know how it went and give it a ⭐️ rating! Your feedback helps us to make more recipes you really want.