Heat the oil in a pan. Sauté the onion and garlic. Briefly cook the tomato puree, add the tomatoes and all the other ingredients up to and including the pepper, simmer uncovered for approx. 10 mins. Mix in the basil.
Spread the gnocchi and peas in the prepared baking dish. Top with the tomato sauce. Scatter the mozzarella over the top.
Approx. 20 mins. in the centre of an oven preheated to 200°C. Remove from the oven, garnish with basil.