Heat olive oil in a large pan. Fry the chorizo until it releases its red oil.
Peel and chop the onion and garlic.
Remove the seeds from the pepper and chop into small pieces.
Add onion and cook until softened, then stir in garlic.
Add red pepper, smoked paprika if using, and rosemary. Stir well.
Pour in chopped tomatoes and stock (plus red wine if using). Season. Bring to a gentle simmer.
Simmer gently for 20 minutes.
Stir in butter beans and cook for 10 minutes more, until the sauce has thickened and the beans are soft
Garnish with parsley and serve with crusty bread.