1
The day before you plan to serve the dish, cover the beans in cold water and leave to soak overnight
2
The next day, add the olive oil to a large, heavy-bottomed saucepan over a low heat. Add the onion and cook for a few minutes until softened
3
Drain the beans and add them to the saucepan. Stir, pour in 2 litres of water and bring to a simmer. Add a little salt (but not too much – it’s easier to season the dish properly later) and cook uncovered for 1 hour
4
Add the potatoes to the pot along with the farro (or barley) and the sage leaves. Cook for another hour, or until the soup becomes thick and creamy. If the soup becomes too dry, top up with a little water
5
Taste the soup and add salt to taste. To serve, spoon into bowls and finish with a drizzle of olive oil and a sprinkling of black pepper
