Preheat the oven to 180˚C, gas mark 4. Heat the oil in a large ovenproof casserole dish, sauté pan or frying pan over a high heat. Add the meatballs, season and fry for 5 minutes until browned all over. Meanwhile, strip the chard leaves from the stalks.
Finely slice the chard stalks and add to the pan with the garlic; fry for a minute. Pour in the passata, add the oregano sprigs, then season (you may want to add a pinch of sugar too). Transfer the uncovered pan to the oven for 15 minutes.
Remove the pan from the oven and stir in the mascarpone. Tear the chard leaves into large strips and stir into the sauce. Return the pan to the oven for 5 minutes, then serve with couscous or pasta, if liked.
Cook’s tip
For a one-pot meal, stir a pouch of ready-cooked freekeh or can of drained butter beans into the sauce along with the chard leaves, before baking for the final 5 minutes.