Heat the butter and oil in a heavy-based pan and sauté the celery, potato and leeks until they are beginning to soften.
Add a splash of water – about two tablespoons – season, and cover the pan. Sweat for about 20 minutes, adding a little more water occasionally to keep it moist.
Stir in the stock, cider and more seasoning. Bring to the boil, then simmer for 15 minutes. Leave to cool completely and purée the soup in batches.
Return the soup to the pan. Before serving, heat it as soon as your toasts are ready, add the cream, heat through and check the seasoning.
Toast the bread lightly and spread with butter. Divide the cheese between the slices, put them on to a grill pan and toast until the cheese is bubbling (how long this takes depends on how powerful your grill is – domestic grills vary hugely).
Cut the apples into slices and melt about 20g of butter in a frying pan. Sauté the slices until they are slightly golden on both sides – they don’t have to be completely soft, a little crunch is good.
Toss in the thyme and divide the apples between the toasts. Drizzle with a little honey and grind black pepper on top.