Remove the skins from the sausages and discard. Add the sausage meat to all the other meatball ingredients in a mixing bowl. Using your hands, mix well together and shape into 8 to 10 meatballs. Set aside.
Heat 1 tablespoon olive oil in a frying pan and cook the meatballs until no longer pink in the middle. Drain on kitchen paper then set aside.
For the tomato and mushroom sauce:
In a medium sized saucepan heat 2 tablespoons olive oil and sweat down the onions for approximately 7 minutes, add the garlic and cook for another 1 to 2 minutes.
Add the remaining ingredients, except the basil, and bring to the boil. Reduce heat down to a simmer and cook gently for 10 to 15 minutes.
Add the meatballs to re-heat in the sauce and mix well. Garnish with basil and serve.
Depending on the brand of tinned tomatoes used you may need to add a little sugar the sauce. Taste first.
If you wish, the meatballs can be made well in advance and browned so that they can be reheated in step 6.