In a pan, sauté the onion and chorizo until soft and fragrant. Add minced garlic and cook for 30 seconds.
Stir in the tomato paste until the raw taste disappears.
Add fresh tomatoes and butter beans with their juices. Season with salt and let it simmer for 10-15 minutes or until tomatoes are soft and cooked through.
In a mortar and pestle, bash 1 garlic clove with a pinch of salt. Add toasted pine nuts and mash into a paste. Incorporate fresh basil leaves, then drizzle in olive oil and season with salt and pepper.
Use a hand blender to mash a couple of ladles of the bean mixture. Stir back into the pan to thicken.
Serve the stew with basil pesto, a drizzle of extra virgin olive oil, and your favorite bread.
