Wash the silverbeet / Swiss chard, and remove the stalks. Place in a large heatproof bowl and pour over boiling water to cover. Leave for 2 minutes, until wilted. Drain.
Mix together the ricotta, mozzarella, parmesan and garlic with a little black pepper.
Once the silverbeet / Swiss chard is cool enough to handle, squeeze out as much of the excess water as you can. Roughly chop then add to the cheese and stir well to combine.
Divide the pizza dough into four. Take on piece of dough and roll out on a lightly floured board to a diameter of 18 cm (7 inches).
Take a quarter of the filling and place on one half of the dough, leaving approx 2 cm / ¾ inch around the edges to allow for sealing the calzone. Fold the dough over the filling to create a parcel and pinch the edges together to seal.
Repeat with the remaining dough and filling.
Place the calzones on the baking sheets, leaving space in between the calzone. Cut three small vents in the top of each calzone with a sharp knife to allow steam to escape, then brush with a little olive oil and sprinkle with a little salt.
Place in the preheated oven and bake for 18-20 minutes, until golden brown.
Leave for 5 minutes before serving - the calzones are very hot inside!Serve on their own or with marinara or tomato sauce (see my recipe in notes for a quick tomato sauce.) Best served soon after baking, although leftovers will keep in the fridge, covered, for up to 2 days.