Slice the onions, carrots and celery. I like to get the carrots pretty small, as I don't personally like big chunks of carrot, but realise cutting them small can test your patience.

Fry the onion in nice big drizzle of oil, after a couple minutes add the carrots, and then the celery. I'm not trying to cook them through, just to soften them a little at this stage.

Mince the garlic, and add to the pan. I like to make a little well in the middle with a little more oil, and cook the garlic for roughly a minute, as I don't want it to burn.

Now transfer the contents of the pan to the slow cooker. Add a generous tablespoon of tomato paste, and the passata. I like to mix half a stock cube with hot water, pour this in to the passata container, and swirl it around before pouring in the slow cooker, this gets the last of the passata left in the container. Finally add the meatballs in, and set the slow cooker to low.

Now cook your spaghetti so it is slightly hard, I usually aim for 1 minute less than the packet recommends. Drain, and then add back into the hot pan with a couple ladles of the sauce. Keep stirring through, making sure to coat all of the spaghetti with the sauce. Then distribute it into bowls, topping up with extra sauce, the meatballs, and freshly chopped Basil.