Warm Swedish blueberry drink (Blåbärssoppa)

1. Put the blueberries (fresh or frozen) into a pan with most of the water and the sugar and bring to the boil.

2. Simmer over low heat for 5 minutes so the berries soften and release their juice.

3. For a completely smooth drink, blend with a hand blender and push through a sieve; in the traditional version the berries stay whole.

4. Mix the starch with the remaining cold water until smooth.

5. Pour it into the hot blueberry liquid in a thin stream, stirring constantly, and bring just to the boil until it thickens slightly and turns glossy; don't cook it any longer.

6. Serve warm in mugs or cold in glasses.

Tip: Blåbärssoppa is the drink of Swedish cross-country skiers: at the refreshment stations of Vasaloppet, the world's longest cross-country ski race, hot blueberry drink is handed out by the litre. It isn't a real soup but a thick, drinkable fruit beverage that gives quick energy. Cold, it's also a great summer refresher, and you can control how thick it is with the amount of starch.