Heat the oil in a large pan and fry the onion until soft. Add the pancetta and fry for 5 minutes. Add the mince, oregano and garlic and fry until lightly browned.
Mix in the mushrooms, tomatoes, balsamic vinegar and 100ml water. Reduce the heat and simmer gently for 30 minutes, stirring every so often. For the last 5 minutes, cook the gnocchi following pack instructions, then drain.
Preheat the oven to 180°C, fan 160°C, gas 4.
Pour the mince into an ovenproof dish. Top with the gnocchi, sprinkle over the cheeses and bake in the oven for 15 minutes until the cheese is melted and golden.