Drain the soaked beans and add to a large saucepan along with the ½ onion and 2 garlic cloves. Cover with water and boil for 30-40 minutes, uncovered until tender (it may take longer depending on the beans). Drain and discard the garlic and onion.

Finely chop, grate or press the remaining 2 garlic cloves.

To a pan, add the oil over medium-low heat. Add the garlic and sage, cook for 1 minute, don’t burn. Stir in the tomatoes, salt and pepper and baking soda. Cook for 10 minutes.

Stir in the beans and taste for seasoning. Cook for a further 5 minutes and allow to sit for 10 minutes before serving. If the sauce gets too thick, add a small amount of water. Taste for salt, add more if needed. Serve warm.