Mix together the mince, Parmesan, pesto, egg yolk and breadcrumbs in a bowl. Roll the mixture between damp palms to make 20 balls.
Heat the oil in a frying pan. Add the meatballs and cook for 2–3 minutes until browned all over. Remove from the pan and set aside on kitchen paper to drain.
Add the onion and garlic to the pan and fry for 2–3 minutes. Add the tomatoes, bring to the boil and simmer for 5 minutes.
Add the meatballs to the pan with the cream and cook for a further 5 minutes. Stir in the torn basil leaves.
Serve the meatballs with the sauce, accompanied by pasta and green salad, if liked.