Peel and coarsely grate the onion with a cheese grater (or finely chop). Peel and grate all of the garlic. Drain and rinse the butter beans. Destem and chop the greens.
Heat the olive oil in a frying pan over medium heat. Add the onion and cook for 2-3 minutes until soft. Add one clove of garlic, harissa, tomato puree and water. Stir and simmer for 2 minutes.
Tip in the butter beans and stir to coat. Simmer for 6-8 minutes until thickened. Season to taste.
In a separate pan, heat the remaining oil. Add the garlic and greens. Cook, stirring for 2-4 minutes until wilted.
Spoon the harissa beans onto plates. Top with garlicky greens and serve with flatbreads or rice.
