Heat the olive oil in a large, heavy-bottomed pan or Dutch oven over a medium-high heat. Add the sausages and cook for 8-10 minutes, turning occasionally, until they are browned and crisp on all sides. They don't need to be cooked through at this stage. Remove them with tongs and set aside on a plate.

Reduce the heat to medium. Add the sliced onions to the same pan, scraping up any browned bits from the bottom. Cook for 5-7 minutes, stirring occasionally, until they have softened and are turning translucent.

Add the sliced peppers to the pan. Continue to cook for another 10 minutes, stirring every so often, until the peppers have softened considerably and are starting to get a little colour on the edges.

Stir in the minced garlic, dried oregano, and smoked paprika. Cook for just one minute more until the garlic is fragrant. Be careful not to let it burn. What works best for me is to make a little well in the centre of the vegetables and cook the garlic there briefly before stirring it all together.

Pour in the white wine or chicken stock to deglaze the pan. Let it bubble away for a minute or two, scraping the bottom of the pan with a wooden spoon to lift any remaining flavourful residue.

Stir in the tomato passata, tomato purée, and the optional sugar. Season with a good pinch of salt and several grinds of black pepper. Bring the sauce to a gentle simmer.

Return the browned sausages to the pan, nestling them into the pepper and onion mixture. Reduce the heat to low, cover the pan with a lid, and let it simmer gently for 15-20 minutes, or until the sausages are cooked through and the sauce has thickened slightly.

Remove from the heat. Check the seasoning and adjust if necessary. Stir through most of the chopped fresh parsley, saving a little for garnish. Let it rest for 5 minutes before serving.