400 g (13 oz) can borlotti or haricot beans, drained and rinsed
125 g (4 oz) fresh or defrosted green beans, cut into 2.5-cm (1-inch) lengths
50 g (2 oz) Parmesan-style cheese, grated
salt and pepper
Cook the new potatoes in a saucepan of lightly salted boiling water for about 10 minutes, until just tender. Drain and cool slightly, then cut into 5-mm (1/4-inch) slices.
Meanwhile, heat 2 tablespoons of oil in a large, deep-sided frying pan and cook the onion for 2 minutes. Add the celery and cook for a further 2 minutes, then add the garlic and cook for a final 2–3 minutes, stirring frequently, until lightly golden.
Stir the pesto into the onions, then add the diced tomatoes, stock, borlotti beans and green beans. Season generously with salt and pepper and bring to the boil, reduce the heat and simmer for 5 minutes, until the tomatoes soften and the beans are tender.
Tip the vegetable mixture into a large ovenproof dish, and arrange the sliced potatoes over the top. Sprinkle with the grated cheese, drizzle with the remaining oil and cook under a preheated grill for 7–8 minutes, until golden.