Heat the oil in a nonstick frying pan and cook the onions for 5 minutes, then add the garlic and cook for a further 3 minutes, until soft and golden. Add the smoked paprika for the final 30 seconds, then remove from the heat.
Meanwhile, toast the pine nuts in a small, dry frying pan for 2–3 minutes, until lightly golden, shaking the pan frequently to prevent burning.
Tip the beans into a food processor with the lemon juice, half the chives and the onion mixture. Season well, then pulse briefly, adding enough yogurt to make a rough-textured pâté.
Spread the pâté on to hot toast and scatter with the toasted pine nuts and remaining chives. Serve immediately with celery sticks.