Peel the onions and carrot. Finely chop them both. Trim and finely chop the celery.
Pour 1 tbsp olive oil into a large pan and warm on a medium -high heat. Add 4 sausages (save the other 2 in the pack for breakfast) and brown for about 2 mins on each side, then transfer to a plate.
Turn the heat down under the pan slightly and add the onions, carrot and celery. Season well with salt and pepper. Sweat for 5 mins to soften, stirring occasionally.
While the veg cooks, peel and thinly slice the garlic. Add to the pan with the tin of cherry tomatoes. Drain the cannellini beans, rinse and add them too. Pour in 150ml cold water and stir together. Bring to the boil.
Return the sausages to the pan. Partly cover with a lid and simmer for 20 mins till the sausages are cooked through and the sauce has thickened slightly. Taste and add more salt and pepper if you think it needs it.
Tear up the basil leaves and stir half through the stew. Ladle into bowls and scatter the remaining basil leaves over the top to serve.