Czech sour lentils with fried egg (Čočka na kyselo s vejcem)

1. Pick over and rinse the lentils and (unless they're a quick-cooking variety) soak for 2 hours. Drain, bring to the boil with 1 litre of fresh water and the bay leaves and simmer gently for 25-35 minutes until tender but not falling apart; salt at the end of cooking.

2. In a small pan, sweat the finely chopped onion in two-thirds of the butter for 5 minutes until translucent, sprinkle over the flour and toast, stirring, for 2-3 minutes until light golden.

3. Whisk the roux smoothly into 200 ml of cold water, pour into the lentils and cook, stirring, for 5 minutes until thickened.

4. Season with the vinegar, sugar and pepper until pleasantly sour – the sourness is the point, so taste boldly; remove the bay leaves.

5. Fry 4 eggs in the remaining butter so that the yolks stay runny.

6. Spoon the lentils into deep plates, slide a fried egg on top and serve with pickled gherkins and fresh bread.

Tip: "Čočka na kyselo" is a favourite of meat-free weekdays in Czech canteens and pubs; it's also often served with frankfurters (párky) – for a meatier version, fry a couple alongside.