Melt half of the butter with the 2 tablespoons (40ml) of olive oil in a large, deep-frying pan (or stockpot) over medium heat. Stir in the onion and cook until softened. Add the zucchini (courgette). Cook, stirring, for a few minutes until the zucchini has softened. Season with sea salt to taste. Stir in the rice and after 2 minutes, pour in the white wine. Cook, stirring, until all the liquid has been absorbed.
Add a ladleful of the hot stock, stirring constantly. When the stock has been absorbed, stir in another ladleful. Continue to add ladlefuls of stock, stirring and allowing each ladleful to be absorbed before adding the next until the rice is ‘al dente’ (approximately 15 minutes).
Remove the frying pan (or stockpot) from the heat. Stir in the remaining butter and Parmigiano Reggiano – buon appetito.