Remove the dish from the slow cooker and put on the hob and put it on a medium heat. Add a little oil and add the sausages.
Chop the onions and add them to the pan when the sausages are cooked. Put them on a lower heat to soften them.
Remove the sausages and chop into chunks.
Turn the slow cooker on to a medium heat and put the dish back inside.
Chop the garlic, celery, carrots and potatoes (above 3cm squares) and add to the pan.
Boil the kettle and make up stock using the stock cubes and about 500ml of water and add to the slow cooker with the red wine.
Add the passata and stir in the celery leaves and rosemary.
Season with salt and pepper.
Leave on a medium heat for 5-6 hours. Giving it a stir when you can and topping up with a bit of water if it needs it.
Enjoy with a glass of red wine.