A basic favorite of mountain regions, soups based on split peas (or sometimes lentils) appear all over the Alps. This one features celeriac, that favorite Central European root, for extra flavor.

• 5 ounces split yellow peas
• 1 small celeriac root
• 2 or 3 potatoes
• 1 onion
• 1 tablespoon of butter or lard
• 1 scant tablespoon plain flour
• 2 1/4 pints ham stock

Soak the split peas overnight in cold water.

Pour away the water, cover peas with ham stock from which all the fat has been removed, add a sprig of thyme, and cook until the peas are soft.

Chop the onion very finely; peel and dice the potatoes and the celeriac.

Melt the butter or lard in a thick saucepan, add the onions and leave them to soften without browning. Then add the cubed celeriac and potatoes, and simmer until the vegetables are cooked but still firm. Dust with flour and brown everything together lightly.

Sieve the peas to a puree: then add the puree and liquid to the vegetables. Blend well, gently reheat, adjust seasoning and serve.

There are various embellishments which may be added to this soup -- a little cream or sour cream floated in the center of each soep bowl, perhaps with a sprinkling of finely diced ham or crisply fried bacon, or simply some chopped chives.

To turn the soup almost into a main course, add some sliced Frankfurter sausages.

Serves four.