Preheat oven to 180°C.
Heat a non-stick frying pan over medium heat. Cook the onion in the oil until golden, add the spinach, garlic and lemon rind. Cook for another 2-3 minutes then remove from heat and cool slightly.
Mix together the cream cheese, parmesan and spinach mixture. Season with salt and pepper.
Slice each chicken breast in half along the middle. Pound lightly between sheets of baking paper until they are thin steaks.
Lay each chicken steak out and spoon over a couple of teaspoons of spinach mixture. Fold over and use toothpicks to enclose and secure.
Place the flour, egg and breadcrumbs into separate bowls. Season the flour with salt and pepper.
Working on at a time, dust each chicken bomb in flour, dip in egg, and then gently coat in breadcrumbs. Place on a lined baking tray and refrigerate for 15 minutes.
Shallow fry the bombs until golden brown, remove and drain on a paper towel then place on a lined baking tray and transfer to the oven. Continue cooking until fully cooked through.
Carefully remove the toothpicks before serving and slice each bomb in half. Serve with salad or steamed vegetables.