To make the meatballs, heat the oil in the frying pan and gently fry the onion for a few minutes to soften.
Add the garlic to the pan and cook for a minute to brown.
Put the cooked onion in a bowl with all the other meatball ingredients and mix together with your hands until well combined.
Shape the mixture into table tennis size balls (I got about 16 meatballs), set on a plate and then chill for 20-30 minutes to firm up.
Preheat the oven to 180’C
Toss the onion, courgette and pepper with the olive oil and roast for 30 minutes – stirring half way through.
Stir in the tomatoes and lay the meatballs on top, return the dish to the oven for 20 minutes.
Give the mixture another stir and the return to the oven for a further 10 minutes.
Finally, remove the dish from the oven, stir in the ketchup until everything is well combined and then dob the mascarpone all over the top.
Return the pan to the oven and bake for 10 minutes.
Remove from the oven and serve with couscous and salad.