Peel and finely chop the onion. Clean and wash the green beans. Heat 1 tablespoon of oil in a pot. Fry the onion in it. Sauté tomato paste in it. Deglaze with 3/4 l water, bring to the boil. Stir in stock. Covered green beans and cook for about 15 minutes
Drain the beans, rinse and drain. Peel the garlic. Wash the basil and pluck off all but a few leaves for garnishing. Finely chop pine nuts, garlic and basil, e.g. in a universal chopper. Mix well with the remaining oil, season with salt and pepper
Heat the beans in the soup. Season bean soup with salt and pepper. Serve with the pesto and garnish with remaining basil
Instead of basil, you can also prepare the pesto with flat parsley: chop finely with pine nuts and garlic, add oil