Peel the red onions and finely chop them. Peel and crush or finely chop the garlic cloves. Pick the thyme leaves off the woody stalks and roughly chop the leaves. Scrub the carrots and roughly chop them. Slice the chestnut mushrooms into 1cm slices.
Toss the cardamom pods into a pestle and mortar and crush till the seeds pop out. Discard the papery husks. No pestle and mortar? No problem. Simply pop the cardamom into a sturdy bowl and use a jam jar or the end of a rolling pin to bash the pods open.
Pour 1 tbsp oil into a pan and bring to a medium heat. Slide in the onions and garlic. Sprinkle in a little salt and pepper and cook for 3 mins, stirring occasionally. Stir in the thyme, cardamom and bay leaf and cook for a further 5 mins.
Pour in the passata and stir in the sliced mushrooms. Simmer for 5 mins.
Drain the beans and rinse well with cold water. Stir into the pan along with the chopped carrots. Crumble in the stock cube and cover with 1 ltr boiling water. Give everything a good mix and bring to a simmer. Cook for 20 mins till the carrots are tender.
Just before serving, finely chop the flat leaf parsley. Stir into the bean stew. Have a taste, and add more salt and pepper if needed. Ladle into deep bowls and serve.