Pre-heat the oven to Gas 6, 200°C, fan 180°. Heat the oil in a casserole dish and brown the sausages for 5 minutes.
Add the onion, carrot, celery and pepper to soften. Add a little more oil if you need to and cook for 10 minutes.
Dissolve the stock cube in a mug of boiling water and add to the pot with the tinned tomatoes, cannellini beans, tomato puree, bay leaf and oregano. Bring to a simmer.
Cook in the oven with the lid on for 30-40 minutes. Stir in the pesto and serve immediately.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.