Peel, wash and cut the celery into small cubes. 1⁄2 Bring l water and stock to the boil, cook celery in it for about 4 minutes. Drain and collect the stock.
Peel and finely chop the onion. Heat butter in a pot and fry diced onion until transparent. Dust with flour and sauté until light brown. Add stock and milk while stirring, bring to the boil and simmer for about 5 minutes.
Grate cheese and stir into the soup. Add celery and season to taste with salt, pepper and nutmeg.
Fry ham in a coated pan without additional fat until crispy. Wash the chives, shake dry and cut into small rolls. Break the ham into small pieces. Serve soup with ham and chives.
Roasted farmhouse bread tastes good with it.