Peel and finely chop the onion. Trim and scrub the carrot and celery. Finely chop them both (no need to peel the carrot). Warm a large pan for 1 min. Add 1 tbsp olive oil and the chopped veg. Season with salt and pepper. Cover. Sweat over a low heat for 8-10 mins till softened.
Peel and finely chop the garlic. Strip the leaves from a few of the thyme sprigs. Finely chop the parsley leaves and stalks. Add the garlic, 2 tsp of the thyme leaves and most of the parsley into the veg. Add the bay leaf. Drain the beans. Add them. Crumble in the stock cube and pour in 600 ml boiling water (or use hot homemade stock). Simmer for 5 mins to heat everything through.
While the soup simmers, strip the thick cores from the kale leaves. Roughly chop the leaves. Add to the pan and simmer for 5 more mins to wilt the kale. Taste and add more salt, pepper and thyme leaves if you think it needs it. Serve in warm bowls with a scattering of the remaining thyme sprigs.