Heat a large frying pan over a low heat. Add the pine nuts and gently toss for 30 seconds to a minute. Remove the pine nuts from the pan and set aside.
Heat the oil in the same frying pan over a medium-high heat and cook the onion for 1 minute, then add the mince and cook for a further 5 minutes, until lightly browned.
Add the sweet potato and cook for 5 minutes, returning the pine nuts for the final 2 minutes.
Add the passata and tomato purée and simmer for 15 minutes, until reduced to a thick sauce.
Season with freshly ground black pepper, then stir through the grated courgette and set aside to cool. Tear the mozzarella ball into pieces and stir into the cooled mince.
Preheat the oven to 200°C, fan 180°C, gas mark 6. Lightly oil a baking tray.
Make up the pizza base mix according to pack instructions. Divide the dough into 4 pieces, then knead each into a ball on a lightly floured surface.
Roll out into circles, each measuring about 18cm in diameter.
Using just half of the mince mixture, spoon a quarter of it into the middle of each circle.
Brush the edges of the dough with a little water, fold over to form a crescent and crimp the edges together with your fingers to seal.
Brush the tops of the folded pizzas with the beaten egg, then bake for 20 minutes, until golden and heated through. Serve with the bistro salad on the side.
Cook's tip: You only need half the mince filling for this recipe. Let the rest cool completely and keep in the fridge to have as a pasta sauce for lunch the next day. Or, buy an extra 2 packs of pizza dough mix and make another 4 calzones. Freeze uncooked. Cook from frozen at 200ºC, fan 180ºC, gas mark 6 for 30-40 minutes, until piping hot.