Preheat the oven to 200 °C / 400 °F / Gas Mark 6. Cut the cheese into slices, arrange the cheese slices over slices of bread or baguette, put in the oven and bake for a few minutes until the cheese is golden and melted. Cut the toasts into smaller pieces, if you wish.
Wash the lettuce and spin dry in a salad spinner, season to taste with salt and pepper.
Cut the celery stalks into slices.
Core the apple and cut into slices, mix with a tablespoon of lemon juice.
Toast the walnuts and pumpkin seeds in a dry pan until lightly browned and fragrant, transfer on a plate (they can easily burn).
Pour the dressing ingredients into a small jar, close the lid and shake vigorously until a thick sauce is created.
Arrange the lettuce onto plates, top with cheese toasts, celery and apple slices, sprinkle with nuts and pour over the dressing.