The most common liquids used to make soup are either water or stock, but in countries where simple cheeses are made at home with the aid of an acid rather than rennet, there is another option. Rather than discarding the whey from cheese making, this slightly sour liquid can be turned into soup by thrifty cooks.

I was reminded of this when reading a recent article in Epicure on homemade ricotta which advises to tip out the whey after draining the curd. Not on my watch you don't. Why throw something down the sink that's full of vitamins and minerals essential to good health and has a pleasant taste to boot?

In eastern European countries such as Poland, there are quite a few soup recipes that have serwatka (whey) as the base, to which they add such things as raisins or potato or beetroot. In a nice closing of the circle, there is one soup made from whey and sour cream, thickened with egg yolks and poured over rice topped with the homemade cheese.

Serwatka is incorporated into marinades as a meat tenderizer and also used to braise meats such as pork ribs and goose. It goes into bread making and sauces and if you've had too much to drink, neatly doubles up as a hangover remedy!

You may notice in cooking with whey that tiny dots of curd will materialize when you bring it to a simmer. This is nothing to worry about and gives a nice speckled finish to the soup.

Homemade Ricotta
(adapted from Epicure)

9 cups whole milk
1 cup buttermilk
1 tablespoon salt
2.5 tablespoons distilled vinegar

In a large pot, mix the milk with the buttermilk and leave at room temperature for 2 hours. For a slightly sweeter (and quicker) cheese, you can omit this step. Bring the milk/buttermilk mixture to 85 degrees celsius and remove from the heat. Stir in the vinegar and salt and leave stand for 10 minutes. Line a colander with muslin over a bowl and with a skimmer, gently lift the curd into the lined colander until none is left. Reserve the whey. Place the drained ricotta into a covered container and keep in the fridge for up to 4 days.

Whey Soup

1 onion, finely diced
25g unsalted butter
200g finely sliced mushrooms
200g kaiserfleisch, cut into lardons
3 skinless chicken thighs, cubed
2 potatoes, diced
10g dried porcini, soaked in boiling water
1 fermented cucumber, not pickled, grated
4 tablespoons chopped dill, a little reserved for garnish
reserved whey from ricotta
salt & fresh ground pepper

Gently sweat the onion in the butter until completely soft but in no way browned. Raise the heat and add the mushrooms, kaiserfleisch and chicken and cook until lightly coloured. Add the potato, finely chop the porcini and add along with the soaking water, grated fermented cucumber and chopped dill, pour in the reserved whey and season with salt & fresh ground pepper, bring to a simmer and cook for about 30 minutes and serve garnished with a little extra dill.