In a blender, whizz the bread into breadcrumbs, tip into a bowl and set aside. Pulse the beans and tip out into another bowl, adding the egg, spinach, thyme, cheddar, garlic, nutmeg and seasoning. Stir in half the breadcrumbs. Shape into 4 burgers (2 large, 2 small) and coat with the remaining breadcrumbs.
Wash and shred the baby gems and halve the tomatoes. Combine the crème fraîche, mayonnaise, pesto and lemon juice in a jug. Mix the lettuce and tomatoes in a salad bowl and drizzle over the dressing.
Heat the oil in a frying pan. Add the burgers and fry for 2-3 minutes on each side, or until they turn golden. Remove and keep warm. Serve the burgers with the salad and crusty bread.
Cook's tip: these burgers freeze really well so will make a great standby supper.